Apparatus for forming a nanostructured thin film with porosity gradient on an array of sloped outdoor panel surfaces using meniscus drag

ABSTRACT

A thin-film coating applicator assembly is disclosed for coating substrates in outdoor applications. The innovative thin-film coating applicator assembly is adapted to apply performance enhancement coatings on installed photovoltaic panels and glass windows in outdoor environments. The coating applicator is adapted to move along a solar panel or glass pane while applicator mechanisms deposit a uniform layer of liquid coating solution to the substrate&#39;s surface. The applicator assembly comprises a conveyance means disposed on a frame. Further disclosed are innovative applicator heads that comprise a deformable sponge-like core surrounded by a microporous layer. The structure, when in contact with a substrate surface, deposits a uniform layer of coating solution over a large surface.

CROSS REFERENCES TO RELATED APPLICATIONS

This application refers and includes material from U.S. Pat. No.10,010,902 filed on Sep. 26, 2016 entitled “Thin-film coating apparatusfor applying enhanced performance coatings on outdoor substrates”, andU.S. Pat. No. 10,574,180 filed on May 15, 2016 entitled “Sensor forMeasuring Reflected Light for Optimizing Deposited PerformanceEnhancement Coatings on Substrates”, and U.S. patent application Ser.No. 15/129,403 filed on Sep. 26, 2016 entitled “Low Temperature CurableEnergy Transmission Enhancement Coatings Having Tunable PropertiesIncluding Optical, Hydrophobics and Abrasion Resistance”, thedisclosures of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

This invention relates to the application of nanostructured thin filmson outdoor surfaces.

BACKGROUND

Silicon photovoltaic panels typically have a protective top layer ofcover glass or plastic to protect the underlying photovoltaic cells.Enhanced performance coatings such as thin-film energy transmissionimprovement layers in the form of antireflective coatings on the topsurface of the cover glass or plastic protective layer is desirable fromthe standpoint of increasing solar cell efficiency. Such films improvethe transmission of infrared, visible and ultraviolet wavelengths oflight through the cover glass or plastic protective layer, typically byproviding a refractive index gradient to better capture incident lightenergy that otherwise would be reflected from the surface of the coverglass or plastic protective layer. Enhanced transmission of light energyto photovoltaic cells provides an advantage by increasing the number ofphotons available for electricity production. Energy transmissionimprovement coatings, again in the form of antireflective coatings, mayalso provide an advantage for glass windows by reducing the lightreflected off of the surface, reducing the glare normally emanating fromglass surfaces. Increased energy transmission, in the form of increasingthe number of photons transmitted through the glass from outside abuilding to the inside of the building, may also reduce the need forinterior electric lighting. Both photovoltaic panel cover glass andwindow glass are typically large and require even coatings of uniformthickness to be effective.

Thin film coating technologies have been developed and perfected forindustrial scale production in window and solar panel manufacturing. Asit has become known that thin-film antireflective coatings improve solarcell efficiencies, it has become desirable to now manufacture solarphotovoltaic panels with such coatings in recent years. However,retrofitting older panels not originally coated with antireflectivecoatings requires dismantling of the photovoltaic array and sending theindividual panels to a factory or facility for coating, an expensive anddisruptive endeavor. Similarly for glass window panes installed oncommercial buildings and storefronts, many may benefit from an antiglarecoating, but are already installed and would need to be replaced withnew pre-coated window panes, or by installing anti-glare sheets on thepane. Currently, there are no viable, cost effective solutions forretrofitting photovoltaic panels and window panes with high qualitythin-film coatings.

Currently available light reflection sensors are not capable ofmeasuring the light reflection from a relatively large spot size on thetop surface of solar panels installed in the field and comparing theresults before and after application of a performance enhancementcoating. The very small spot size analyzed by a typical sensor using afiber optic probe is insufficient to accurately measure in one readingan area large enough to determine the average performance across thewhole solar panel of solution deposited performance enhancing coatings.This is due in part because variations in the top surface structure ofsolar panel cover glass and variations in solution deposited coating maynot be adequately represented within the very small spot size read bythe fiber optic probe. Multiple readings by such a probe would have tobe done to develop a statistically significant number of samples toestimate average coating performance.

Furthermore, typical fiber optic probe sensors require the use of aseparate computing device, such as a laptop computer, to run thecalculations required to produce human readable data. The process oftaking numerous measurements and transporting and setting up a typicalfiber optic sensor with a separate computing device for each solar panelto be measured is relatively cumbersome and time consuming compared witha device with integrated computing and human readable display that candetermine the average performance difference in light reflectionproperties by taking just one measurement before and just onemeasurement after application of a performance enhancement coating.

Energy transmission enhancement coatings are thin-film dielectricoptical coatings that augment the transmission of infrared, visible andultraviolet light to surfaces of transparent and non-transparentsubstrates. Enhanced transmission of light energy to photovoltaic cellsprovides an advantage by increasing the number of photons available forelectricity production. Energy transmission improvement coatings, againin the form of antireflective coatings, may also provide an advantagefor glass windows by reducing the light reflected off of the surface,reducing the glare normally emanating from glass surfaces. Increasedenergy transmission, in the form of increasing the number of photonstransmitted through the glass from outside a building to the inside ofthe building, may also reduce the need for interior electric lighting.Such coatings serve to reduce reflected light, and increase transmissionby acting as a refractive index-matching layer, forming a gradient ofrefractive index from that of air to that of the substrate, within alayer approximately ¼ wavelength in thickness, where the wavelength bandof light may be chosen by adjusting the thickness and the material ofthe coating. Thin dielectric films formed on a reflective surface canprovide a refractive index match between the substrate and thesurrounding medium, typically air, if the film has a refractive indexintermediate between the substrate and air. In addition, a thin filmnecessarily presents more than one reflective interface from whichincident light can reflect to create destructive interference conditionssuppressing the light reflected from each interface.

Anti-reflective (AR) thin films or coatings are examples of such energytransmission enhancement coatings To this day, the optical principlesoriginally laid out by Rayleigh and others to explain the AR effectgovern the design objectives of modern engineered AR thin film coatings.Modern thin-film deposition methods and nanotechnology are employed toproduce advanced coatings. Present commercial coatings comprise bothsingle and multilayer coatings, which may be deposited by so-called drydeposition techniques, such as RF sputtering or vapor depositiontechniques (i.e., magnesium fluoride), or by wet methods. Sol gelmethods are particularly used as wet deposition techniques, and are ableto be carried out in non-laboratory environments, do not requireexpensive high-vacuum systems, and use inexpensive starting materials.

Recent efforts have produced advanced AR coatings, and optical coatingsin general, where attention is paid to optimizing mechanical propertiesas well as optical properties. Examples of improved AR coatings areabundant in many recently published patent applications and issuedpatents. These more advanced coatings rely on multilayer wet depositioncomprising an adhesion layer, followed by one or more engineered opticallayers that are by themselves mechanically weak. By focusing onoptimizing optical properties, many commercial AR coatings suffer frominferior mechanical properties, such as low abrasion resistance,brittleness, short lifespan and low thermal/chemical stability.

Many optical layers for use as AR coatings may comprise nanoparticles,particularly hollow nanoparticles to effectively provide a nanoporousmedium of low refractive index for improved reflection suppression.Furthermore, the optical layers may be capped by a protective layer toensure mechanical protection of the entire coating from environmentalstresses experienced by the substrate. Some of these protective layersfeature organo-silicate cross-linking components combined withsilicate-based sol gels to form the protective layers. In all cases, themanufacture of multiple layer coatings is inherently more expensive andcomplicated in comparison to application of a single layer. [0006], Inmany coating processes, curing temperatures for producing opticalcoatings such as AR coatings are typically carried out well above 100°C., typically over 500° C., to have a reasonable curing times. This maylimit or preclude the production of scratch-resistant AR coatings ondelicate substrates, or heat-sensitive substrates made from polymers,layered semiconductor photovoltaic structures, and low melting metals,such as aluminum. Furthermore, the high curing temperatures preclude thepossibility of applying optical coatings outside of a manufacturingenvironment, where specialty ovens or heat treating assembly lines arenecessary to applying and baking optical coatings on large substratessuch as photovoltaic panels. Efforts have been made to make availableless expensive liquid sol-gel coating precursor solutions for panelmanufacture, and in recent years many new panels are produced with ARcoatings.

In many cases, older photovoltaic and solar thermal panels that do nothave an AR coating have been part of a working installation, such as amulti-panel solar array, for a number of years. As such panels have manyyears of service lifetime left, it may be desirable to retrofit thesepanels with the newer sol-gel optical coatings, such as AR coatings,taking advantage of their lower costs, to increase the solar energyconversion efficiencies by 3-4 percentage points. Over time for largearrays, these small increases in conversion efficiency translate tosignificant increases in profit margins for commercial operations.However, the curing conditions required by present day commerciallyavailable sol-gel coating precursor solutions involve high temperaturebaking regimes of approximately 200° C. to over 500° C. in order toproduce sufficiently robust optical coatings. These high-temperatureconditions thus require dismantling of the installation in order todeliver the panels to a special facility or return them to the factoryof origin to reprocess the panels with the optical coatings. Theendeavor is highly disruptive and costly both in downtime and processingcosts. Ideally, the panels could be coated on site, without the need todismantle them and ship them off-site. If a low-temperature curingformulation could be developed, whereby the heat of the sunlightcaptured by the substrate can be harnessed to cure a precursor sol-gelsolution to high quality optical coatings in a relatively short time, onpanels in an existing outdoor installation. As an example, sun-curing atambient air temperatures ranging from 10° C. to 40° C. combined withincident solar radiation can heat the surface of the substrate totemperatures ranging from about 30° C. to over 100° C. For such anapplication, a low-temperature curable coating composition that resultsin a highly robust optical coating is required, where in addition to thelow-temperature curability, the resulting coating film has very highabrasion durability, humidity resistance, and high optical transmittanceover a large spectral range.

No examples are currently available describing a single layer opticalcoating having both optimized optical and mechanical characteristics andthat cures at temperatures less than 100° C. Moreover, no example of anoptical coating method or process exists to produce a single layeroptical coating with tuned optical, mechanical and chemical propertieson demand, whereby the important properties can be easily tuned to meetthe environmental demands of the substrate.

SUMMARY OF THE INVENTION

Herein is described an apparatus for forming a nanostructured thin filmwith a porosity gradient on an array of sloped panel surfaces outdoors.The meniscus drag mechanisms may be considered alternate embodiments of,or a subset of, the coating applicator heads described below.

Combinations of material may include, but not be limited to thefollowing:

-   -   Incorporation of the deformable porous core and capillary        interface layers with the meniscus drag mechanism.    -   Combination of the surface conforming means and mechanisms and        force absorbing and leveling means and mechanisms with the        meniscus drag mechanism and/or applicator.    -   Integration of adjustable width support structures and one or        more meniscus drag mechanisms to enable compatibility with        different width panels.    -   Incorporation of one or more pump, tubing and manifold or plenum        embodiments and the meniscus drag mechanism.    -   Integration of mechanisms and methods shown below with the        mechanisms and methods also shown below.    -   Incorporation of the control loop feedback means and mechanisms        for controlling the applicator, meniscus drag mechanisms and/or        coating deposition method and/or processes.    -   Combination of the reflection sensor, photo-detector, and/or        spectrometer means and mechanisms with the reflection sensing        device.    -   Incorporation of the various embodiments of the single-layer        energy transmission enhancement coating of into coating        deposited by the applicator.    -   Integration of one or more of the various curing means of the        single-layer energy transmission enhancement coating into the        apparatus and/or method of forming a nanostructured thin film.    -   Incorporation of the mechanisms, means and methods for tuning        the coating into the mechanisms, means and methods of forming a        nanostructured thin film.    -   Incorporation of one or more of the constituents in the        formulation into the coating solution and/or nanostructured thin        film.    -   Incorporation of the durability, robustness and/or performance        characteristics of the coating into the nanostructured thin        film.

The invention described herein is an apparatus for forming ananostructured thin film with a porosity gradient on an array of slopedpanel surfaces outdoors. The apparatus comprises an applicator whichtranslates across the array of sloped outdoor panel surfaces and usesmeniscus drag deposition to deposit onto the sloped outdoor panelsurfaces a solution comprising various solvents and amorphous silicawhich then forms a nanostructured thin film with a porosity gradientdependent at least in part on the evaporation of the various solvents.

The innovation described herein is a novel portable coating apparatusfor applying performance enhancement coatings to the surfaces ofutilitarian substrates such as photovoltaic (solar) panels, glasswindows, and the like, used outdoors or inside buildings. Embodiments ofthe innovative coating apparatus comprise manually controlled andautonomous portable coating assemblies, wherein the entire assembly, ora portion thereof, is adapted to travel, translate, or otherwise beconveyed along a substrate surface while spreading an even and uniformlayer of a liquid coating solution, which then cures to form a solidcoating layer. The coating may be an optical coating, as, for example,an anti-reflective coating, advantageous for increasing efficiencies ofphotovoltaic panels and solar thermal panels, or reducing glare fromglass window panes.

It is a primary object of the innovation described herein to provide afacile means of applying coatings of field installations of substratespost-manufacture, as, for example, an array of photovoltaic panelsinstalled outdoors at a power generation facility, an array of solarthermal panels installed on a building roof or in another outdoorlocation, and the like. As coatings such as anti-reflective coatings areproven to increase efficiencies of photovoltaic panels in particular andhave begun to gain wide acceptance in recent years, it may beadvantageous to retrofit older panels already deployed in installationswith such coatings; however, present coating systems are stationaryapparatuses for use in a manufacturing facility, for example, and thecurrent post-manufacture coating protocol requires the dismantling of aphotovoltaic (or other) array and sending the panels to a facility tohave the coating done. This is obviously expensive and disruptive, wherethe costs of going this route may outweigh the efficiencies gained bythe coating, at least in the short term. The instant innovation providesa desirable solution to this dilemma, whereby a portable coating systemis provided having the ability to traverse the surface of a panelsubstrate and deposit a high-quality coating across the entire surfaceof the substrate. By high quality, it is understood that the filmsdeposited by the instant innovation are substantially uniform inthickness across the substrate.

To achieve such uniformity in coating thickness, the instant innovationis adapted to be placed on or over a panel substrate, and then to causethe coating mechanism to traverse the panel while spreading the coatingsolution at a substantially constant deposited volume per panelsubstrate unit area. For some coating applications, some embodiments ofthe instant innovation may comprise a portable coating assembly adaptedfor coating installed panel substrates of the type described above,wherein the portable coating assembly comprises a support structurehaving dimensions that are compatible with panel dimensions (e.g., thewidth of the support structure is compatible with the width of thepanel). Some portable coating assembly embodiments may further compriseone or more coating applicator mechanisms or structures and a conveyancemechanism that is adapted to move the one or more coating applicatormechanisms along their trajectory on the surface of the panel substrate.

The inventive portable coating assembly further comprises one or moreinnovative coating applicator mechanisms affixed to the supportstructure. In some embodiments, the support structure may take the formof a platform. The coating applicator mechanisms comprise a means todeposit the coating solution on the surface of the substrate, said meansincluding, but not limited to spray heads, rollers, slots, brushes,doctor blades, wipers, draw-bars, sponges, foam, porous textile layer ora combination of such.

In some embodiments, the coating applicator mechanisms comprise one ormore applicator heads, each of which further comprises a deformable corebody, composed of a compliant and deformable material, and a microporous“skin”, or interface layer having a certain micropore volume sufficientto hold a determined amount of liquid coating solution and contacting aportion of the surface of the deformable core body. The deformable corebody may also be porous in nature and serve the function of anadditional reservoir for a liquid coating solution, and the microporouslayer serves the function of an interface between the deformable corebody and the substrate surface, whereby the micropores act as acapillary array to transfer coating solution to the substrate. In someembodiments, a textile such as a felt fabric may be used as themicroporous interface layer. Felt fabrics have a large plurality offibers oriented randomly within the fabric, where the interstitialspaces between the fibers present an extensive array of tortuousmicropores.

Moreover, felts can be fabricated from a large variety of fibers tovirtually any thickness, and have very fine and soft textures ideal foruniform spreading of liquids on surfaces. The soft and compliant natureof felts make them ideal for use as a microporous interface layer. Inaddition to felts, other fabrics and materials may be used for the samepurpose (e.g. woven sheet and high porosity foam). The micropores of thefelt interface or an interface created by other materials effectivelyact as an array of capillaries that store and transfer liquid coatingsolution to the surface in a manner that is substantially uniform overthe contact surface of the applicator head or other suitable coatingmechanism. As coating solution is depleted in the microporous interfacelayer, in one embodiment where the deformable core is also porous andcontains coating solution, the microporous interface layer may drawcoating solution from the deformable core and transfer it to thesubstrate surface. In another embodiment, coating solution may be pumpedfrom a reservoir through one or more tubes to the microporous interfacelayer before or during the coating process.

The instant innovation includes manually guided and automatedembodiments, and combinations thereof. Manually guided embodiments ofthe instant innovation comprise the support structure and coatingmechanism assembly discussed above, further comprising a handleextension of the support structure that may be rigid or bendable, wherethe latter may comprise springs in the handle to compensate forvariations in hand-applied pressure, which can lead to non-uniformitiesin coating thickness. Handles may also be pivotally attached to theinventive portable coating assembly, providing ergonomic deployment ofthe invention. Automated embodiments may comprise mechanized or roboticcoating assembly versions, whereby the support structure and coatingmechanism assembly may further comprise a conveyance mechanismcomprising a motorized drive.

An example of this type of embodiment is an electric motor affixed tothe support structure, and coupled to a roller axel via a chain, belt ora gear train, whereby the roller axle may be connected to wheels orother devices to convey the coating assembly across the substrate. Theelectric motor may be controlled by an electronic motor control circuitin some embodiments. In other embodiments, the electronic motor controlcircuit programmable, and in yet further embodiments may also be capableof wireless control and programming. As an example, the motor serves thefunction of driving the innovative portable coating assembly at aconstant speed to enable deposition of coatings having substantiallyuniform thicknesses in one embodiment. As a further example, if athickness gradient is desired across the substrate, the motor can beprogrammed to ramp the speed of the assembly in another embodiment. In astill further embodiment, a ramped or variable speed may also be desiredfor maintaining a substantially uniform coating thickness in possibleembodiments where the coating solution flow rate is also ramped orvariable.

In automated embodiments, the electronic motor control circuit may alsoreceive input from sensors that measure parameters that may correlatewith the motor speed necessary to maintain a substantially uniformthickness. Such measured parameters may include ambient temperature,ambient humidity, or amount of light reflection from the coated surface.The electronic motor control circuit may then use these measuredparameters to adjust the motor speed. In this way, a substantiallyuniform coating thickness may be maintained even if the measuredparameters may change over time.

In some embodiments, the effective width of the support structure issufficient to span the width of a panel substrate, requiring only asingle excursion of the innovative portable coating assembly in onedirection along the length of the substrate to deposit the coating,simplifying the coating process. In other embodiments, a motorized drivemechanism may translate the coating applicator mechanism both lengthwiseand widthwise across the substrate in a grid fashion or other motion,for example, when coating areas are wider than the width of the supportstructure. In other embodiments, the effective width of the supportstructure is adjustable to span the width of substrates ofnon-standardized widths. Related to this aspect, manual, partiallyautomated or fully automated embodiments may include an elongated handlefor manual placement and removal of the innovative portable coatingassembly on a substrate. The elongated handle provides extended reach,and as such may have ergonomic value.

Moreover, the handle may be pivotally affixed to the support structure,providing further ergonomic value. In other embodiments, the supportstructure may be positioned on to or translated across the substrate bya robotic arm. In yet other embodiments, the support structure may beautonomously translated across the substrate by an on-board motorwithout the use of a handle or robotic arm to guide it. In yet otherembodiments, a combination between manually guided and automatedfunctions may include a handle whereby the operator may help control anymotion in an axis orthogonal to the direction of coating while theautomated motorized functions may guide the portable coating assembly inthe direction of coating. In yet further embodiments, a cabledtranslation mechanism may be employed.

It is a further objective of the innovation to provide coatings ofuniform thickness. For embodiments comprising one or more coating heads,each of which further comprises a deformable core body, the degree ofdeformation may be a function of the weight of the entire assemblysupported by the coating heads when engaged with the surface to becoated, as well as other vertical forces imposed on the innovativeassembly. The weight of the portable coating assembly may also besupported in part by the conveyance mechanism. The deformation mayfurthermore pressurize any liquid contained within the microporousinterface layer, and if a porous deformable core body is used, anyliquid contained within the porous deformable core body as well,increasing the flux of the liquid when discharged to the substratesurface during the coating process.

While the weight of the portable coating assembly may remainsubstantially constant during the coating process, fluctuations invertical forces, for instance, those due to changes in hand or armpressure fluctuations that may occur when the portable coating assemblyis manually guided during the excursion in manual embodiments, may causefluctuations in deposition rate of the coating. Therefore, randomvariations in coating thickness result, if measures are not taken tomitigate these fluctuations. In some embodiments, coating mechanisms maybe attached to the support structure by force-absorbing strut membersresponsive to changes in vertical force, mitigating them to variousextents. In one type of embodiment, the struts are in the form of leafsprings. In other embodiments, struts comprise spring-loadedarticulating joints interposed between elongated members, rigid ornon-rigid. In yet further embodiments, struts may be in the form of ashock-absorbing dashpot mechanism, or simple compression springs.

The spring constants, or stiffness, of the various types of strut springcomponents may be chosen to cause the spring to deform sufficiently inresponse to the magnitude of changes in applied force. The struts thenmay absorb or at least partially absorb force fluctuations orredistribute and mitigate these force fluctuations over time beforethese are transferred to the deformable porous core bodies of thecoating mechanisms, causing fluctuations in the geometry and thereforethe pressure on the liquid contained within. As mentioned above, thesechanges translate to variations in the flux of coating solution beingdischarged from the porous core or the microporous interface layer,ultimately resulting in variations in coating film thickness.

In the embodiments described in the preceding paragraph, theforce-absorbing struts connect the coating heads to the supportstructure. In alternative embodiments, struts may connect the conveyancedevice to the support structure, whereas the coating mechanisms may beeither suspended by more rigid members, or again connected byforce-absorbing members. In other embodiments, the coating mechanismsmay be connected to the support structure by means of hinged brackets orslides which minimize the transfer of vertical forces from the supportstructure to the coating heads during the coating process.

In some embodiments, coating solution may be charged to the one or morecoating heads in a continuous or discontinuous manner, for instance byan on-board pumping system, and in other embodiments, the coating headsare charged continuously or discontinuously by an offline means.Reducing complexity, weight and expense of the innovative portablecoating assembly, offline transfer of coating solution to the coatinghead or heads is a preferable solution, whereby the pumping system andcoating solution reservoir is eliminated from the assembly. To this end,a separate charging or re-filling station may be provided. In oneembodiment, a charging station comprises a frame or superstructure, adosing platform, a receiving structure to place the innovative portablecoating assembly, whereby the receiving structure is adapted to positionthe coating heads of the innovative portable coating assembly on thedosing platform. Other methods of charging the coating heads areembodied by continuous and intermittent on-board or off-board pumpingsystems.

In addition to anti-reflective coatings, this invention may be used todeposit other performance enhancement coatings, including wave-lengthshifting coatings and filter coatings such as “Low-E” coatings thatminimize the transmission of either ultraviolet light or infrared lightor both. In other embodiments, the performance enhancement coating maybe a multi-functional coating, providing a combination of two or morefunctions, including, but not limited to anti-reflection, wavelengthshifting, filtering of ultraviolet or infrared or both, anti-soiling,self-cleaning or thermal energy management.

The innovation described herein is a novel portable coating apparatusfor applying performance enhancement coatings to the surfaces ofutilitarian substrates such as photovoltaic (solar) panels, glasswindows, and the like, used outdoors or inside buildings. Embodiments ofthe innovative coating apparatus comprise manually controlled andautonomous portable coating assemblies, wherein the entire assembly, ora portion thereof, is adapted to travel, translate, or otherwise beconveyed along a substrate surface while spreading an even and uniformlayer of a liquid coating solution, which then cures to form a solidcoating layer. The coating may be an optical coating, as, for example,an anti-reflective coating, advantageous for increasing efficiencies ofphotovoltaic panels and solar thermal panels, or reducing glare fromglass window panes.

It is a primary object of the innovation described herein to provide afacile means of applying coatings of field installations of substratespost-manufacture, as, for example, an array of photovoltaic panelsinstalled outdoors at a power generation facility, an array of solarthermal panels installed on a building roof or in another outdoorlocation, and the like. As coatings such as anti-reflective coatings areproven to increase efficiencies of photovoltaic panels in particular andhave begun to gain wide acceptance in recent years, it may beadvantageous to retrofit older panels already deployed in installationswith such coatings; however, present coating systems are stationaryapparatuses for use in a manufacturing facility, for example, and thecurrent post-manufacture coating protocol requires the dismantling of aphotovoltaic (or other) array and sending the panels to a facility tohave the coating done. This is obviously expensive and disruptive, wherethe costs of going this route may outweigh the efficiencies gained bythe coating, at least in the short term. The instant innovation providesa desirable solution to this dilemma, whereby a portable coating systemis provided having the ability to traverse the surface of a panelsubstrate and deposit a high-quality coating across the entire surfaceof the substrate. By high quality, it is understood that the filmsdeposited by the instant innovation are substantially uniform inthickness across the substrate.

To achieve such uniformity in coating thickness, the instant innovationis adapted to be placed on or over a panel substrate, and then to causethe coating mechanism to traverse the panel while spreading the coatingsolution at a substantially constant deposited volume per panelsubstrate unit area. For some coating applications, some embodiments ofthe instant innovation may comprise a portable coating assembly adaptedfor coating installed panel substrates of the type described above,wherein the portable coating assembly comprises a support structurehaving dimensions that are compatible with panel dimensions (e.g., thewidth of the support structure is compatible with the width of thepanel). Some portable coating assembly embodiments may further compriseone or more coating applicator mechanisms or structures and a conveyancemechanism that is adapted to move the one or more coating applicatormechanisms along their trajectory on the surface of the panel substrate.

The inventive portable coating assembly further comprises one or moreinnovative coating applicator mechanisms affixed to the supportstructure. In some embodiments, the support structure may take the formof a platform. The coating applicator mechanisms comprise a means todeposit the coating solution on the surface of the substrate, said meansincluding, but not limited to spray heads, rollers, slots, brushes,doctor blades, wipers, draw-bars, sponges, foam, porous textile layer ora combination of such.

In some embodiments, the coating applicator mechanisms comprise one ormore applicator heads, each of which further comprises a deformable corebody, composed of a compliant and deformable material, and a microporous“skin”, or interface layer having a certain micropore volume sufficientto hold a determined amount of liquid coating solution and contacting aportion of the surface of the deformable core body. The deformable corebody may also be porous in nature and serve the function of anadditional reservoir for a liquid coating solution, and the microporouslayer serves the function of an interface between the deformable corebody and the substrate surface, whereby the micropores act as acapillary array to transfer coating solution to the substrate. In someembodiments, a textile such as a felt fabric may be used as themicroporous interface layer. Felt fabrics have a large plurality offibers oriented randomly within the fabric, where the interstitialspaces between the fibers present an extensive array of tortuousmicropores.

Moreover, felts can be fabricated from a large variety of fibers tovirtually any thickness, and have very fine and soft textures ideal foruniform spreading of liquids on surfaces. The soft and compliant natureof felts make them ideal for use as a microporous interface layer. Inaddition to felts, other fabrics and materials may be used for the samepurpose (e.g. woven sheet and high porosity foam). The micropores of thefelt interface or an interface created by other materials effectivelyact as an array of capillaries that store and transfer liquid coatingsolution to the surface in a manner that is substantially uniform overthe contact surface of the applicator head or other suitable coatingmechanism. As coating solution is depleted in the microporous interfacelayer, in one embodiment where the deformable core is also porous andcontains coating solution, the microporous interface layer may drawcoating solution from the deformable core and transfer it to thesubstrate surface. In another embodiment, coating solution may be pumpedfrom a reservoir through one or more tubes to the microporous interfacelayer before or during the coating process.

The instant innovation includes manually guided and automatedembodiments, and combinations thereof. Manually guided embodiments ofthe instant innovation comprise the support structure and coatingmechanism assembly discussed above, further comprising a handleextension of the support structure that may be rigid or bendable, wherethe latter may comprise springs in the handle to compensate forvariations in hand-applied pressure, which can lead to non-uniformitiesin coating thickness. Handles may also be pivotally attached to theinventive portable coating assembly, providing ergonomic deployment ofthe invention. Automated embodiments may comprise mechanized or roboticcoating assembly versions, whereby the support structure and coatingmechanism assembly may further comprise a conveyance mechanismcomprising a motorized drive.

An example of this type of embodiment is an electric motor affixed tothe support structure, and coupled to a roller axel via a chain, belt ora gear train, whereby the roller axle may be connected to wheels orother devices to convey the coating assembly across the substrate. Theelectric motor may be controlled by an electronic motor control circuitin some embodiments. In other embodiments, the electronic motor controlcircuit programmable, and in yet further embodiments may also be capableof wireless control and programming. As an example, the motor serves thefunction of driving the innovative portable coating assembly at aconstant speed to enable deposition of coatings having substantiallyuniform thicknesses in one embodiment. As a further example, if athickness gradient is desired across the substrate, the motor can beprogrammed to ramp the speed of the assembly in another embodiment. In astill further embodiment, a ramped or variable speed may also be desiredfor maintaining a substantially uniform coating thickness in possibleembodiments where the coating solution flow rate is also ramped orvariable.

In automated embodiments, the electronic motor control circuit may alsoreceive input from sensors that measure parameters that may correlatewith the motor speed necessary to maintain a substantially uniformthickness. Such measured parameters may include ambient temperature,ambient humidity, or amount of light reflection from the coated surface.The electronic motor control circuit may then use these measuredparameters to adjust the motor speed. In this way, a substantiallyuniform coating thickness may be maintained even if the measuredparameters may change over time.

In some embodiments, the effective width of the support structure issufficient to span the width of a panel substrate, requiring only asingle excursion of the innovative portable coating assembly in onedirection along the length of the substrate to deposit the coating,simplifying the coating process. In other embodiments, a motorized drivemechanism may translate the coating applicator mechanism both lengthwiseand widthwise across the substrate in a grid fashion or other motion,for example, when coating areas are wider than the width of the supportstructure. In other embodiments, the effective width of the supportstructure is adjustable to span the width of substrates ofnon-standardized widths. Related to this aspect, manual, partiallyautomated or fully automated embodiments may include an elongated handlefor manual placement and removal of the innovative portable coatingassembly on a substrate. The elongated handle provides extended reach,and as such may have ergonomic value.

Moreover, the handle may be pivotally affixed to the support structure,providing further ergonomic value. In other embodiments, the supportstructure may be positioned on to or translated across the substrate bya robotic arm. In yet other embodiments, the support structure may beautonomously translated across the substrate by an on-board motorwithout the use of a handle or robotic arm to guide it. In yet otherembodiments, a combination between manually guided and automatedfunctions may include a handle whereby the operator may help control anymotion in an axis orthogonal to the direction of coating while theautomated motorized functions may guide the portable coating assembly inthe direction of coating. In yet further embodiments, a cabledtranslation mechanism may be employed.

It is a further objective of the innovation to provide coatings ofuniform thickness. For embodiments comprising one or more coating heads,each of which further comprises a deformable core body, the degree ofdeformation may be a function of the weight of the entire assemblysupported by the coating heads when engaged with the surface to becoated, as well as other vertical forces imposed on the innovativeassembly. The weight of the portable coating assembly may also besupported in part by the conveyance mechanism. The deformation mayfurthermore pressurize any liquid contained within the microporousinterface layer, and if a porous deformable core body is used, anyliquid contained within the porous deformable core body as well,increasing the flux of the liquid when discharged to the substratesurface during the coating process.

While the weight of the portable coating assembly may remainsubstantially constant during the coating process, fluctuations invertical forces, for instance, those due to changes in hand or armpressure fluctuations that may occur when the portable coating assemblyis manually guided during the excursion in manual embodiments, may causefluctuations in deposition rate of the coating. Therefore, randomvariations in coating thickness result, if measures are not taken tomitigate these fluctuations. In some embodiments, coating mechanisms maybe attached to the support structure by force-absorbing strut membersresponsive to changes in vertical force, mitigating them to variousextents. In one type of embodiment, the struts are in the form of leafsprings. In other embodiments, struts comprise spring-loadedarticulating joints interposed between elongated members, rigid ornon-rigid. In yet further embodiments, struts may be in the form of ashock-absorbing dashpot mechanism, or simple compression springs.

The spring constants, or stiffness, of the various types of strut springcomponents may be chosen to cause the spring to deform sufficiently inresponse to the magnitude of changes in applied force. The struts thenmay absorb or at least partially absorb force fluctuations orredistribute and mitigate these force fluctuations over time beforethese are transferred to the deformable porous core bodies of thecoating mechanisms, causing fluctuations in the geometry and thereforethe pressure on the liquid contained within. As mentioned above, thesechanges translate to variations in the flux of coating solution beingdischarged from the porous core or the microporous interface layer,ultimately resulting in variations in coating film thickness.

In the embodiments described in the preceding paragraph, theforce-absorbing struts connect the coating heads to the supportstructure. In alternative embodiments, struts may connect the conveyancedevice to the support structure, whereas the coating mechanisms may beeither suspended by more rigid members, or again connected byforce-absorbing members. In other embodiments, the coating mechanismsmay be connected to the support structure by means of hinged brackets orslides which minimize the transfer of vertical forces from the supportstructure to the coating heads during the coating process. In someembodiments, coating solution may be charged to the one or more coatingheads in a continuous or discontinuous manner, for instance by anon-board pumping system, and in other embodiments, the coating heads arecharged continuously or discontinuously by an offline means. Reducingcomplexity, weight and expense of the innovative portable coatingassembly, offline transfer of coating solution to the coating head orheads is a preferable solution, whereby the pumping system and coatingsolution reservoir is eliminated from the assembly. To this end, aseparate charging or re-filling station may be provided. In oneembodiment, a charging station comprises a frame or superstructure, adosing platform, a receiving structure to place the innovative portablecoating assembly, whereby the receiving structure is adapted to positionthe coating heads of the innovative portable coating assembly on thedosing platform. Other methods of charging the coating heads areembodied by continuous and intermittent on-board or off-board pumpingsystems.

In addition to anti-reflective coatings, this invention may be used todeposit other performance enhancement coatings, including wave-lengthshifting coatings and filter coatings such as “Low-E” coatings thatminimize the transmission of either ultraviolet light or infrared lightor both. In other embodiments, the performance enhancement coating maybe a multi-functional coating, providing a combination of two or morefunctions, including, but not limited to anti-reflection, wave-lengthshifting, filtering of ultraviolet or infrared or both, anti-soiling,self-cleaning or thermal energy management.

The instant innovation is a single-layer energy transmission enhancementcoating having tunable optical (transmittance), hydrophobicity (moistureresistance) and hardness (abrasion resistance) characteristics. Theenergy transmission enhancement coatings are a class of optical coatingsincluding, but not limited to, quarter wavelength anti-reflective (AR)coatings, where the thicknesses may be on the order of several hundrednanometers. In addition, the instant innovation provides forlow-temperature coating and curing process for applying a novel liquidsol-gel precursor coating solution formulation that results in theinstant single-layer coating with the enhanced properties. Bysingle-layer, it is meant that the final coating is substantiallycompositionally uniform across its thickness. When describing thecoating process, it may be indicated that a single pass or double passis used to deposit the coating precursor solution. According to theinstant innovation, it is to be understood that this terminology mayindicate that compositionally or structurally heterogeneous layers aredeposited, as is commonly done in the art. According to the innovation,a multiple pass deposition process, such as a double pass, involvescoating two or more layers of the same or different precursor solutionof the same or different composition, resulting in a energy transmissionenhancement coating that may or may not be substantially compositionallyand structurally uniform across its thickness. Thus the term “singlelayer” is used throughout this disclosure to describe the resultinginnovative energy transmission enhancement coating as beingsubstantially compositionally and structurally uniform across itsthickness. In other instances, the coating prepared by a multiple passprocess may be non-uniform across its thickness. It is an object of theinstant innovation that the energy transmission enhancement coating iscurable at low temperatures. For example, the inventive coating solutionmay be cured at 50° C. for 8 hours and provide excellent abrasionresistance. The 50° C. for 8 hours in duration may occur all in one timeperiod or it may occur cumulatively over several time periods. This iscontrasted to more conventional coating compositions that requiresubstantially more time to cure at such low temperatures or that may notcure at all at such low temperatures, resulting in films that may havepoor abrasion resistance. As a result of the excellent performance ofthe low temperature curing process, the invention provides forsun-curable AR coatings, allowing for, as an example, retrofitting asolar panel installation in the field with durable AR coatings wherebythe coating is cured only by passive solar thermal energy. In analternative embodiment, the inventive coating may cure due to chemicalenergy contained within the coating solution itself and not requiresolar thermal energy.

The cured coating layer may comprise hollow-spherical and/or solidsilica nanoparticles or nanospheres that comprise a size distributionranging from 2-200 nm. In all cases the cured coatings of the instantinnovation comprise a cross-linked silica matrix incorporating into itsstructure at least one siloxane agent in the form of a hard coat oranother chemical component that enhances the robustness of the coating.The afore-mentioned components are mixed as sol-gel coating precursorsin the liquid state, and then deposited onto a substrate in the liquidstate by various deposition means with a subsequent curing process toproduce a durable coating ranging between 50 nm and 250 nm in thickness,whereby the deposition process and composition of the precursor coatingsolution are tunable to enable desired spectral characteristics.Accordingly, the inventive optical energy transmission enhancementcoating can be prepared with a range of predictable hydrophobicity andabrasion resistance, by variation of the concentration of at least oneof the coating precursors in the coating solution formulation, as wellas the curing process. Preferably, the concentration of the siloxane canbe varied to produce predictable changes in the hydrophobicity anddurability of the inventive coating.

The instant innovation thus provides the advantage of tailoring themoisture resistance (hydrophobicity) and hardness of the coatings bytailoring the coating composition to suit durability requirementsdictated by the particular application to which the substrate issubjected. The coating process may be carried out by a variety ofmethods, including but not limited to: spray-coating, dip coating,roller coating, doctor-blade coating, wiper coating, draw bar coating,sponge coating and brush coating. Furthermore the thickness of the filmmay be tailored by the judicious choice of the coating process andadjustment of coating parameters, including viscosity of the coatingprecursor solution. The inventive optical coating may be prepared as asingle layer coating or in multiple layers. Preferably, the inventiveoptical coating may be prepared by applying a single pass of coatingprecursor solution, or by applying a double pass coating, where thefirst pass is the application of the coating precursor solution, curingor partially curing the first layer, and then applying a second layer ofthe same coating precursor solution, or a different solution, such as ahard coat or another solution that enhances the coating robustness,where the second coating solution may be compositionally distinct fromthe first layer.

For the purposes of this disclosure, the substrate may be a solarphotovoltaic panel, a solar thermal panel, a sheet window glass, aneyeglass lens, or any other transparent or non-transparent object havingat least one reflective surface where it is desired to suppress thereflectivity. In this way, the durability requirements of an energytransmission enhancement coating on, for instance, a photovoltaic orsolar thermal panel may be satisfied by the selection of one set ofcoating precursor component ratios from a coating precursor componentratio continuum disclosed herein to yield coatings of the requisitedurability. Conversely, an energy transmission enhancement coating suchas an AR coating applied to substrates having less stringent durabilityrequirements, said requirements being satisfied by the selection ofanother set of coating precursor component ratios from the samecontinuum of coating precursor component ratios disclosed herein.

It is one aspect of the instant innovation to provide an energytransmission enhancement sol-gel coating that may be applied and curedin the field, where the term “field” indicates application of thecoating to substrates such as solar panels in an outdoor arrayinstallation, where the array can consist of a single panel or multiplepanels. The term “substrate” most commonly indicates panels of the typereferred to above, viz, photovoltaic panels and solar thermal panels,but may also include glass windows installed in structures. Therefore,instant innovation includes a field coating process, and the finishedenergy transmission enhancement coating product produced by theinnovative process. However, the term field may not be limited toout-of-doors environments, and can include indoor installations, orthose existing in an enclosed structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Overview of the apparatus for forming a nanostructured thin filmwith porosity gradient on an array of sloped outdoor panel surfacesusing meniscus drag.

FIG. 2 Flow chart method process steps for forming a nanostructured thinfilm with porosity gradient on an array of sloped outdoor panel surfacesusing meniscus drag

FIG. 3 Cross section of wet film deposited by meniscus drag deposition

FIG. 4 Cross section of nanostructured thin film with a porositygradient

FIG. 5 Example means of translating applicator across the array ofsloped outdoor panel surfaces

FIG. 6 Additional example means of translating applicator across thearray of sloped outdoor panel surfaces

FIG. 7 Example of reflection sensing device for use by the applicatorfor feedback control of the coating deposition process

FIG. 8 An alternate embodiment of a method or use of the apparatuswhereby the coating process is done horizontally.

FIG. 9 An alternate embodiment of an aspect of the apparatus whereby themeniscus drag deposition method is enhanced or replaced by a spraymethod using a wind shield.

FIG. 10 View of a possible embodiment of the portable coating assembly.Oblique view and frontal view shown.

FIG. 11 Detailed view of coating applicator mechanism construction,showing the deformable core and capillary interface layer arrangement.

FIG. 12a Bottom oblique view of deformable core of coating applicatormechanism.

FIG. 12b Top oblique view of coating applicator mechanism assembly,showing lever spring struts disposed for attachment to supportstructure.

FIG. 12c Top oblique view of coating applicator mechanism assembly,showing leaf-spring struts disposed for attachment to support structure.

FIG. 12d Top oblique view of coating applicator mechanism assembly,showing dashpot mechanism struts disposed for attachment to supportstructure.

FIG. 13 Top oblique view of manually controlled embodiment of theinventive portable coating assembly.

FIG. 14 Side view of manually controlled embodiment of the inventiveportable coating assembly, having a flexible handle structure, having abendable leaf spring action to mitigate vertical forces.

FIG. 15 Side view of manually controlled embodiment of the inventiveportable coating assembly, having a flexible handle structure, having abendable lever spring action to mitigate vertical forces.

FIG. 16 Details of motorized drive coupling to drive axle.

FIG. 17 Top oblique view of portable coating assembly service stationembodiment for transferring coating solution to coating applicatorheads.

FIG. 18 View of bottom side of dosing platform component of portablecoating assembly services station.

FIG. 19 Sectional view of alternative embodiment of coating applicatorhead, adapted for delivery coating precursor solution by pumping meansto a distribution manifold built into the coating applicator mechanism.

FIGS. 20a and 20b a) Operational diagram of a photometric sensor. b)zoom view of an illuminated portion of a substrate surface (coated oruncoated) showing surface irregularities and non-uniformities.

FIG. 21 Schematic diagram of an exemplary electronic control systemembodiment for controlling a mobile coating apparatus using both closed-and open-loop feedback.

FIG. 22 Schematic representation of the componentry of the innovativeportable sensor, showing an embodiment comprising a photodetector.

FIG. 23a Schematic representation of the componentry of the innovativeportable sensor, showing an embodiment comprising a spectrometer.

FIG. 23b Schematic representation of the componentry of the innovativeportable sensor, showing an alternate embodiment comprising aspectrometer.

FIG. 24a Operational schematic of the innovative portable sensor.

FIG. 24b Zoom view of an illuminated portion of a substrate surface(coated or uncoated), showing surface irregularities andnon-uniformities

FIG. 25 Mobile coating apparatus example deployed on a photovoltaicpanel, where the innovative portable sensor is mounted on the chassis ofthe apparatus.

FIG. 26 A side-sectional view of an embodiment of the innovativeportable sensor mounted on a coating apparatus.

FIG. 27 Schematic diagram of an electronic control system embodiment forcontrolling a mobile coating apparatus.

FIG. 28. Transmission spectral comparison between coated (inventive ARcoating) and uncoated smooth glass substrate.

FIG. 29 Transmission spectral comparison between coated and uncoatedtextured glass substrate.

FIG. 30 Transmission spectral comparison between coated and uncoatedsmooth acrylate (PMMA) substrate. Upper graph shows comparison of thetransmission spectra of the uncoated and coated substrate, and lowergraph shows % Delta T.

FIG. 31 Results from abrasion scrub test. Comparison of transmissionspectra of virgin single pass coating and same after abrasion scrubtest. See text for test conditions.

FIG. 32 The change in transmittance (% Delta T) of the innovativecoating after the abrasion scrub test. Same substrate as in FIG. 31

FIG. 33 Results from abrasion scrub test on a double-pass coating.Comparison of transmission spectra of virgin double-pass coating andsame after abrasion scrub test.

FIG. 34 Results of HAST testing. A single-pass coating subjected to HASTconditions. See text for test conditions.

DETAILED DESCRIPTION

Referring to FIG. 1, the inventive apparatus for forming ananostructured thin film with porosity gradient on an array of slopedoutdoor panel surfaces using meniscus drag comprises an applicator A100which mounts onto an array of sloped outdoor panel surfaces A101, andthat uses at least one or more meniscus drag deposition mechanisms A102to deposit a solution A103 comprising various solvents, partiallypolymerized siloxanes, and amorphous silica with a wet film thicknessranging from 5 um to 100 um which then forms a nanostructured thin filmA104 comprising nanostructured silica and ranging in thickness from 50nm to 250 nm with a porosity gradient dependent at least in part on theevaporation of the various solvents onto the sloped outdoor panelsurfaces A105. In at least multiple locations across the nanostructuredthin film A104 (ranging across at least 20%-80% or more of thenanostructured thin film A104, the porosity gradient ranges from at most30% porosity nearest at least one of the surfaces of the sloped panelsA105 to at least 60% porosity furthest from the at least one surface ofthe sloped panels A105. The solvents comprising the solution comprise atleast the following, each ranging in percent volume between 1% and 50%:ethanol, propylene glycol methyl ether, and methanol. The porositygradient depends at least in part on the evaporation rates of thevarious solvents. The evaporation rates depend at least in part on thetemperature of the sloped outdoor panel surfaces A105.

Prior to coating, the surfaces of the sloped panels A105 should bethoroughly cleaned with deionized water. The speed of application of thesolution by the at least one or more meniscus drag deposition mechanismsA102 is dependent at least in part on the viscosity of the solution A103which is dependent at least in part on the temperature of at least oneof the surfaces of the sloped panels A105. The speed may be derivedand/or approximated through fluid physics formulas relating theviscosities of the specific mix of solvents and other constituentscomprising the solution to the temperature of the at least one of thesurfaces of the sloped panels A105. Alternatively, the speed may bederived from a table of known relationships between speed and thetemperature of the at least one of the surfaces of the sloped panelsA105 for a given mix of solvents and other constituents comprising thesolution. The applicator A100 may use a temperature sensor to determinethe temperature of the at least one of the surfaces of the sloped panelsA105.

The applicator A100 may translate across the array of sloped outdoorpanel surfaces A101 by use of various motivator mechanisms (see FIG. 5for at least one exemplary embodiment). As the applicator A100translates across the array of sloped outdoor panel surfaces A101, itmay deposit the solution on the at least one of the surfaces of thesloped panels A105 continuously or discontinuously. In the latter case,the applicator A100 may stop at various positions along the array ofsloped outdoor panel surfaces A101 and use either internal referencepoints to determine its position (e.g. encoder signals from a servodrive mechanism) or sensor feedback that detects specific features ofthe array of sloped outdoor panel surfaces A105 such as gaps that mayexist between panel surfaces 106. Such sensor feedback may be providedby through beam sensors, reflection detecting sensors, roller levelswitch sensors, vision system camera sensing means, or other sensingmeans. Alternatively, the applicator may determine its position througha combination of both internal reference points and external sensorfeedback. In some embodiments, in addition to using sensors to detectthe applicator position relative to the panels, the applicator may usesensors for feedback control of the coating process. Such sensors mayinclude temperature sensors, reflection sensors, humidity sensors, solarirradiance sensors, wind speed sensors or other sensors for measuringcharacteristics of the panels, the solution, the nanostructured thinfilm, the ambient environment, the applicator itself or parts of theapplicator or meniscus drag mechanisms, or other key metrics forcontrolling the coating process. In some embodiments, the coatingprocess may be controlled by an algorithm that accounts for the solutionviscosity and/or evaporation rate due to the solution temperature and/orthe panel temperature and/or the wind speed and/or humidity and/or solarirradiance. In other embodiments, the algorithm may incorporate thereflection of the panels before and/or after coating.

In the process of depositing the solution, the at least one or moremeniscus drag deposition mechanisms A102 may need to run off at leastone end of at one of the surfaces of the sloped panels A105 in order todeposit a uniform coating. To accommodate this the applicator A100 mayhave an extension A107 that extends beyond the end of one of thesurfaces of the sloped panels A105 that enables the at least one or moremeniscus drag deposition mechanisms A102 to run off at least one end ofat one of the surfaces of the sloped panels A105. The applicator A100may also need to engage and disengage the meniscus drag mechanism fromat least one of the surfaces of the sloped panels A105. This can beaccommodated by the addition of at least one or more lifting mechanismsthat can lift or lower the at least one or more meniscus drag mechanismsA102 relative to at least one of the surfaces of the sloped panels A105.The at least one or more lifting mechanisms can comprise at least one ormore electric linear motors or pneumatic cylinders. Furthermore, the atleast one or more lifting mechanisms can lift or lower the at least oneor more meniscus drag mechanisms A102 together or independently from oneanother.

The at least one or more meniscus drag mechanisms A102 may be positionednear each other within the applicator A100 or positioned on one side ofthe applicator A100 or positioned apart from each other. In the lattercase, the at least one or more meniscus drag mechanisms A102 may bepositioned on opposite sides of the applicator A100 as shown in FIG. 1.In the former case where the meniscus drag mechanism are positioned neareach other, the applicator may translate across the array of slopedoutdoor panel surfaces A101 a fixed distance approximately equal to thetotal width of the at least one or more of the meniscus drag mechanismsA102 in between one or more coating passes when coating discontinuously.In the case where meniscus drag mechanisms A102 are placed on oppositesides of the applicator A100, the applicator may use an algorithm todetermine how far to translate in between coating passes when coatingdiscontinuously, where not all the translation distances will beapproximately the same between one or more coating passes. The one ormore meniscus drag mechanisms A102 may operate synchronously together orasynchronously from each other.

The nanostructured thin film A104 may have at least one of the followingproperties: anti-reflection; anti-soiling; wavelength shifting;anti-ultraviolet; anti-infrared; low-E; electromagnetic band passfiltering; or a combination thereof. The array of sloped outdoor panelsurfaces A101 may comprise a solar photovoltaic panel array.Alternatively, it may comprise an array of mirrors, glass panels,plastic panels, blackbody absorbers, or some other surfaces. The atleast one or more sloped panels A105 may comprise at least one or moresolar panels. Alternatively, the at least one or more sloped panels A105may comprise at least one or more mirrors, glass panels, plastic panels,blackbody absorbers, or some other panels.

Referring to FIG. 2, one method of using the inventive apparatus forforming a nanostructured thin film with porosity gradient on an array ofsloped outdoor panel surfaces using meniscus drag consists of thefollowing process steps:

-   -   Step 1—Mount applicator on outdoor array of sloped panels;    -   Step 2—The applicator may then move to a first location on the        one or more of the sloped panels;    -   Step 3—(may happen in parallel with Step 2 or Step 9):        Applicator meniscus drag mechanism deposits solution onto at        least one surface of one or more of the sloped panel surfaces;    -   Step 4—(may happen in parallel with Step 3): Applicator        translates meniscus drag mechanism across the at least one        surface of the one or more sloped panel surfaces;    -   Step 5—(may happen in parallel with Step 4): The solution forms        a wet film in the range of 5 um-100 um on the at least one        surface;    -   Step 6—(may happen in parallel with Step 5): Ambient heat causes        the various solvents in the solution to evaporate;    -   Step 7—(may happen in parallel with Step 6): The evaporation of        the various solvents causes the amorphous silica to        self-assemble into a nanostructured thin film ranging from 50        nm-250 nm in thickness with a porosity gradient ranging from        <30% porosity nearest the at least one surface of the sloped        panels to >60% porosity furthest from the at least one surface        of the sloped panels;    -   Step 8—(may happen in parallel with Step 7): The applicator may        then stop depositing solution onto at least one surface of one        or more of the sloped panel surfaces;    -   Step 9—(may happen in parallel with Step 8): The applicator may        then move to a location different than the first location and        repeat the process starting at Step 3.

Referring to FIG. 3, the meniscus drag mechanism A300 deposits asolution A301 comprising various solvents, partially polymerizedsiloxanes and silica on to at least one surface A302 within the array ofsloped outdoor panel surfaces. The meniscus drag mechanism A300 maycomprise a porous material A303 through which solution A301 passesbefore being deposited onto the at least one surface A302 within thearray of sloped outdoor panel surfaces. In another embodiment, theporous material A303 may be in contact with another porous material 304,in which case the solution A301 passes from porous material A303 toporous material A304 before being deposited onto the at least onesurface A302. In some embodiments, porous material A304 may be havegreater capillary attraction than porous material 303. In the lattercase, as solution passes through material A304 and is deposited onto thesurface A302, additional solution may transfer from porous material A303to porous material A304 due at least in part to porous material A304having greater capillary attraction than porous material A303. Bothporous material A303 and porous material A304 may serve as a smallreservoir of solution during the coating process. The meniscus dragmechanism may comprise one or more manifolds to which solution is pumpedor gravity fed by at least one or more tubes from one or more largersolution reservoirs. The one or more manifolds may distribute solutionacross either the porous material A303 or the porous material A304 orboth.

Referring to FIG. 4, the solution A301 from FIG. 3 comprising varioussolvents, partially polymerized siloxanes and silica forms ananostructured thin film A400 with a porosity gradient dependent atleast in part on the evaporation of the various solvents on at least onesurface A401 within the array of sloped outdoor panel surfaces.

Referring to FIG. 5, in at least one embodiment, the applicator A500comprises various motivator mechanisms A503 which may comprise motorizedwheels, rollers, tractor tread, or other motivator means. As shown inFIG. 5, in at least one exemplary embodiment, at least one motivatormechanism A503 (e.g. motorized wheel assembly) is in contact with atleast one top edge of at least one panel A501 within the array of slopedoutdoor panels. This at least one motivator mechanism helps keep theapplicator A500 aligned with the at least one panel A501 and prevents itfrom sliding off the panel due to gravity. Also as shown in FIG. 5, inat least one exemplary embodiment, at least one motivator mechanism A503(e.g. motorized wheel assembly) is in contact with at least one top backedge of at least one panel A501 within the array of sloped outdoorpanels. This at least one motivator means helps keep the applicator A500engaged with the at least one panel A501 during applicator operation.

Referring to FIG. 6, in at least one embodiment, the applicator A600,mounted on at least one panel A601 within the array of sloped panelsoutdoors, comprises at least one motivator mechanism A602 that can movein such a way that in at least a first position, it engages with the atleast one panel A601 and in at least a second position, it does notengage with the at least one panel A601. In at least a first instance,by moving the motivator mechanism A602 to the second position, theapplicator may be mounted on to or removed from the at least one panelA601 in the array of sloped panels outdoors. In at least a secondinstance, by moving the motivator mechanism A602 to the second position,the applicator may translate across the array of sloped panels outdoorsin a way that avoids collisions with support structures or other objectsthat may interfere with the translation of the applicator. In anotherembodiment, multiple motivator mechanisms A602 may be used whereinsometimes all motivator mechanisms A602 are engaged with at least one ormore panels A601, at other times, only some of the motivator mechanismsA602 are engaged with at least once or more panels 601, and at yet othertimes, none of the motivator mechanisms A602 are engaged with at leastone or more panels A601. In this embodiment or another embodiment,sequencing of the movement of the multiple motivator mechanisms A602 toeither engage with the at least one or more panels A601 or not (possiblyincluding the top and/or front and/or back sides of the panels A601) mayenable the applicator A600 to remain aligned with and/or well engagedwith the one or more panels A601 during the coating process (which maygenerate forces or be subject to gravity that might otherwise cause theapplicator A600 to become misaligned or not well engaged with the one ormore panels A601 during the coating process). This sequencing of themovement of the multiple motivator mechanisms A602 may also enable theapplicator A600 to move across the at least one or more panels A601without the motivator mechanisms A602 colliding with any obstacles alongthe applicator's path (such as mounting brackets or other hardware forthe at least one or more panels A601).

Referring to FIG. 7, in at least one embodiment, a reflection sensingdevice A700 is used by the applicator for feedback control of thecoating deposition process. This reflection sensing device A700 maydetect the reflection of one or more panels A707 before and/or aftercoating. The reflection sensing device A700 may detect the reflection ofthe panels A707 at one or more discrete points across the panels A707,or it may detect the reflection of the panels A707 along a line as theapplicator or the at least one or more meniscus drag mechanisms moveacross the panels A707. In one embodiment, the reflection sensing devicecomprises one or more light sources, A701. The one or more light sourcesA701 may comprise one or more lasers, LEDs, or other light emittingdevice. The light emitted from the one or more light sources A701 may beprimarily coherent light or primarily incoherent light. In the case ofthe light being primarily coherent light, one preferred embodiment is touse green light, with a peak wavelength around 570 nm as this isreasonably close to a key wavelength range of interest in manyanti-reflective films, representing a wavelength range of highattenuation in the visible spectrum. In other embodiments, green, red,or blue primarily coherent light may be used or a combination thereof.Alternatively, white light may be used, or a combination of white lightand primarily coherent light of one or more colors. The light emittedfrom the one or more light sources A701 may reflect off the surface ofthe one or more panels A707 and be received by one or more lightdetectors A708. The one or more light detectors A708 can then determinethe intensity and/or spectral characteristics of the reflected light. Inthe case of the panels A707 having already been coated, the lightreflected off the one or more panels A707 will include light reflectedoff of the coating on the one more panels A707. The light reflected offthe one or more panels A707 and received by the one or more lightdetectors A708 may be compared before and after coating to determine theamount of anti-reflection caused by the coating and thus the coatingprocess can be tuned to optimize the coating process and the desiredamount of anti-reflection. The before and after coating reflected lightcomparison and the tuning process to optimize the coating process can bedone manually the applicator human operator or by circuitry and/orsoftware onboard or off-board the applicator. In some embodiments, alight shield A706 can be used to surround the one or more light emittingdevices A701 and the one or more light detectors A708 to prevent ormitigate ambient light from interfering with the operation of thereflection sensing device 700. In such cases, the light A702 emitted bythe one or more light emitting devices A701 can travel through one ormore pass throughs A705 in the light shield A706 and reflect off the oneor more panels A707 and then travel back through one or more passthroughs A705 to be received by the one or more light detectors A708. Insome embodiments, the pass through A705 may comprise glass or othertransparent media to allow the light A702 to pass through, but not dustor other contaminants that could soil the components of the reflectionsensing device A700. In yet other embodiments, one or more additionallight detectors A704 may be used to directly monitor the light A702emitted from the one or more light sources A701 in order for thereflection measurement to compensate for any power fluctuations in thelight sources 701. In some embodiments, a beam splitter may be used todirect part of the light to the one or more light detectors A704 andpart of the light to be reflected off of the one or more panels A707 andback to the light detector A708.

FIG. 8 shows an alternate embodiment of the method or use of theapparatus whereby the process to coat panel array A802 is doneorthogonally to the embodiment shown in FIG. 1. Whereas the method oruse of the apparatus embodiment shown in FIG. 1 shows the meniscus dragmechanisms depositing the coating from the top of the panels to thebottom of the panels, the embodiment shown in FIG. 8 shows the meniscusdrag mechanisms A801 depositing the coating from left to right. In bothembodiments, the coating can also be deposited in the opposite directionas well, that is in FIG. 1 it may be deposited from bottom to top, andin FIG. 8, it may be deposited from right to left. In FIG. 2, theapplicator A800 moves across the one or more panels A804 and depositsthe coating solution A803 using the meniscus drag applicators A801. Thesolution then forms the nanostructured thin film A805 on the one or morepanels 804. The applicator may coat the panels continuously from left toright or right to left, or it may coat non-continuously, moving betweenpanel index marks A806 or other reference point.

FIG. 9 show an alternate embodiment of depositing the coating solutiononto the one or more panels A903 using a spray system A900. The spraysystem A900 may be placed ahead of the meniscus drag mechanisms suchthat the solution is deposited on the one or more panels A903 by thespray system A900 and then the meniscus drag mechanisms such as thoseshown in FIGS. 1, 3, and 8 uniformly distribute the solution across theone or more panels. Alternatively, the meniscus drag system may bereplaced entirely by the spray system A900 to deposit the solution ontothe one or more panels A903. The spray system A900 may comprise a windshield A904 to prevent wind from interfering with the uniform spray A902distribution onto the one or more panels A903. In some embodiments, thespray system may have one or more air movers A905 to aid in the coatingdeposition and/or to minimize excess spray residue or fumes (toxic,explosive or otherwise). The one or more air movers A905 may alsocomprise air filters to capture or filter out excess spray or fumes.

The instant innovation relates to application of liquid performanceenhancing coating precursor solution to large substrates such asphotovoltaic panels. The instant innovation is a portable lightreflectance sensor for non-destructively determining characteristics ofthin film performance enhancing coatings applied to a substrate, suchas, but not limited to, a photovoltaic panel. It is particularlyadvantageous for outdoor installations, where photovoltaic panelsinstalled in arrays or individually may be retrofitted with performanceenhancement coatings, such as, but not limited to, anti-reflectioncoatings. The innovative portable light reflectance sensor provides alight source and a photodetector for measuring light incident on asubstrate surface from the light source, and reflected to thephotodetector. The spot size of the illuminated region of the substrateis at least 1 centimeter square in area, thus averaging over arelatively wide portion of the substrate surface vs. the much smallerspot size of a fiber optic measuring device. A single measurement maythen be representative of the coating. The innovative light reflectancesensor is adapted to measure substrates in the field, and is especiallyadapted for assessing coating quality during the coating process. Theinnovative portable sensor also comprises a signal processing circuitthat performs analysis of the measurements and feeds back status of thecoating to the operator for coating process control.

The coating of such panels may be facilitated by a mobile coatingapparatus, such as detailed in co-pending U.S. patent application Ser.No. 14/668,956, incorporated herein in its entirety. The innovativedetector comprises a light source adapted to illuminate a region of asubstrate with a spot cross-sectional area of at least 1 cm2, at thesubstrate surface, and a photodetector adapted to collect at least aportion of the light reflected from the substrate surface. In oneembodiment, the innovative photodetector further comprises signalprocessing circuitry adapted to digitize the raw analog data collectedby the photodetector. The photodetector may comprise a spectrometer thatresolves the intensity of reflected light as a function of wavelength.In other embodiments, the photodetector comprises a photodiode orphototransistor. Both types may integrate the total light intensity overthe entire capture spectrum of the reflected light. A variation includesthe use of a bandpass filter or cutoff filters to examine a portion ofthe visible or invisible spectrum, the latter referring to the infrared(IR) and the ultraviolet (UV) extensions of the visible spectrum. Inother embodiments, sources having a more narrow range of wavelengths,such as lasers, light emitting diodes (LEDs), cold cathode and heatedcathode gas discharge lamps, such as mercury lamps and inert gasplasmas, may be employed as light sources.

The relatively large spot size of the incident beam provides theadvantage of spatially integrating surface features over the areacovered by the illuminated region covered by the spot. In this way, theinnovative reflectance sensor is further adapted to spatially andtemporally integrate the spectral characteristics of the light reflectedand collected from the illuminated region of the substrate, where thephotodetector is in electronic communication with the signal processingcircuit. The signal processing circuit may be adapted to perform readoperations to capture the signals from the photodetector on receiving acommand signal, and may be further adapted to extract and storedigitized photometric data from the captured sensor signal. In addition,the signal processing circuit may be adapted to perform computations onthe photometric data, and then correlate the data to the one or more ofthe characteristics of the thin film coating on the substrate ofinterest. It is an aspect of one embodiment of the instant innovationthat the correlated characteristics of the coating be transformed intocontrol information to be fed back to either a human operator or to acontrolling device for assessing the quality of the coating as it isapplied from a liquid coating precursor solution, and if necessaryadjusting the coating deposition method, or coating make-upcharacteristics. In this way, the deposition process may be steered toproduce a finished coating having optimal performance.

A coating apparatus adapted to apply a film of liquid precursor solutionthat cures into a finished performance enhancement coating, such as, butnot limited to, an anti-reflection coating, may be used in conjunctionwith the innovative portable reflectance sensor to provide a feedbackcomponent in the control loop of the coating process. The coatingapparatus may be controlled manually by a human operator, orautomatically or semi-automatically by an automated control system. Inthe automatic or semi-automatic cases, the innovative portable sensormay be used as a feedback component in a closed control loop.

It is an aspect of the innovation that the light source produce a lightbeam having a spot cross-sectional area of at least 1 cm2 at thesubstrate surface. Commercially available light sensors based on totalreflection and/or spectral reflection measurements used for measuringthin film or substrate surface characteristics use small spot sizes(typically 1-2 mm in diameter). Many of these devices are designed foruse in measuring surface characteristics of small substrates, such assilicon wafers. For both large and small substrates, multiple readingstaken at several locations on the substrate are generally necessary toobtain a representative sample of coating or surface characteristics.The larger spot size of the instant invention allows integration ofsuperficial properties over an area 50-100 times or larger than thatprovided by conventional fiber optic devices, providing a representativesampling of the local region of the surface from which the light isreflected.

It is another aspect of the invention to provide a means to correlatephotometric data obtained from the light reflected off of a substratesurface and collected by the photodetector. For example, the surface mayhave a previously-cured performance enhancement coating, such as ananti-reflection coating, or a freshly applied liquid coating precursorsolution. Optionally, the surface may be uncoated, where a measurementmay be made to obtain baseline data of initial reflectance for abefore-and-after comparison when a coating is applied. The rawphotometric data collected may provide a measure of the reflectance ofthe substrate surface, as, for example, to measure the attenuation ofpercent reflection after application of an antireflection coating.

Another measurement derived from the raw photometric data may be thethickness and quality of coverage of a fresh layer of coating precursorsolution. The photometric data may be in the form of spectral intensitydata. In this case, the photodetector may incorporate a spectrometerthat can scan over a range of wavelengths. In other embodiments, thephotodetector may be a simple photodiode or phototransistor that isadapted to measure across a broad spectrum of light, and may be used tomeasure intensity integrated over the entire visible, near IR and UVspectrum to which is it sensitive, or a portion thereof, if, as anexample, a bandpass filter is used. It is another aspect of the instantinnovation that this information may be used for feedback control in acoating process control loop for the coating apparatus. The coatingapparatus may be controlled by a human operator in one set ofembodiments, thus the control loop is an open loop, or may bemachine-controlled in another set of embodiments, necessitating a closedfeedback control loop.

The signals may be used to indicate the thickness of a coating. As anexample, a relatively high average reflectance intensity reading and ashift in the reflected spectrum toward the red or infrared side of thelight spectrum may indicate that a performance enhancement coating istoo thick as applied. The operator or automatic control system may needto adjust the speed of the applicator, or decrease coating precursorsolution viscosity. As the spot size is large, variations normallyencountered in both coating non-uniformities and variations in theunderlying substrate surface, such as photovoltaic panel cover glass orphotovoltaic cell surface, are integrated over the spot area andcollected by the photodetector. Thus, the photodetector receives areflection spectrum that is averaged over the relatively large spotsize. The spectral intensity data may be averaged over a range ofwavelengths to determine a predominant component or spectral region. Bysubtracting the reading from one area measured prior to coating from thereading of the same area after coating, variations other than those ofthe coating itself may be canceled out.

Multiple readings may be made, for example, over very large areas whereseveral locations on the substrate surface or multiple substratesurfaces may be sampled. In this way, the uniformity of surfacecharacteristics may be assessed. As an example, for an anti-reflectioncoating, the uniformity of the coating thickness and quality may bequantified. This is particularly advantageous for applying new coatingsto a substrate such as a photovoltaic panel or to multiple substratessuch as a solar panel array. An operator of a coating apparatus may usethe innovative portable reflectance sensor to monitor the quality of thecoating process by measuring the spectral characteristics of thereflected light. As an example of a method of use, an operator of thecoating apparatus may first take baseline measurements on an uncoatedphotovoltaic panel, then apply a thin film of liquid precursor solutionthat will cure to form a finished coating, such as an antireflectioncoating.

The innovative portable reflectance sensor may include signal processingcircuitry comprising an on-board microprocessor and memory, on which maybe stored one or more algorithms and/or look-up tables for correlationof measurements to known film characteristics. As an example, theportable sensor may include a spectrometer that is programmed to scan arange of wavelengths and record spectral intensities. The data may bedigitized and stored as binary data in the on-board memory, where themicroprocessor may compare the intensity data reflected from the freshlyapplied liquid coating to the baseline data taken from the bare(uncoated) surface of the photovoltaic panel. In another embodiment, thedata may also be offloaded to an off-board data storage and retrievalsystem, accessed by the portable sensor using wired or wireless means.

As an example of process control by use of the innovative portablesensor, the comparison algorithm may reveal that the reflection spectralintensities are higher than expected for an antireflection coating, andmoreover that the spectrum measured is shifted toward the red orinfrared side of the spectrum in comparison to an expected reflectionspectrum (for example in comparison with a ¼ wave-thick index matchingfilm). These spectral characteristics may indicate that the coating istoo thick.

A further aspect of the innovation may be the inclusion of an algorithmto present recommendations to the operator as to steps required toadjust the coating process to optimize the coating. Here, the coatingthickness may be a function of applicator speed and viscosity of theliquid coating precursor solution. The coating process may be adjusted,for example, by changing applicator speed, or by changing solutionviscosity. In addition, the coating thickness may be corrected, if foundto be out of specification by measurements taken with the innovativeportable sensor, by applying a make-up coating.

In further embodiments of the innovation, measurements of airtemperature and surface temperatures of the substrate may beincorporated into the portable sensor system design and algorithms.Thermal measurements may be used for further optimization of the coatingprocess, as evaporation rates and curing rates may be taken intoconsideration by the optimization algorithm, preferably stored inon-board memory and executed by an on-board microprocessor, therebyadjusting the recommendations to the operator as to the optimal coatingspeed and solution viscosity, for example. In further embodiments,humidity sensors may also be a part of the sensor array to furtherrefine the coating process, if, as an example, relative humidity affectsthe evaporation rate of the solvent used in the precursor solution, orif humidity affects (or is necessary to initiate) the curing chemistryof the coating.

In other embodiments of the instant innovation, an automated controlsystem may replace the operator of the coating apparatus as being therecipient of the feedback from the innovative portable sensor signalprocessing circuitry. The automated control system may be adapted todirectly respond to the feedback issuing from the innovative portablesensor signal processing circuitry. In one example, the innovativeportable sensor may be mounted on a coating apparatus, and configured tocontinuously or intermittently measure the surface characteristics byrefection spectrometry. In this example, the portable sensor is aimed atthe substrate surface behind the apparatus, so that the freshly coatedsurface may be measured. The characteristics of the freshly appliedcoating may be assessed, and the speed of the coating apparatus may becontrolled by a closed feedback loop. In other embodiments, one portablesensor may be situated in such a way as to measure the substratereflection before coating and another portable sensor may be situated tomeasure the substrate reflection after coating, with the difference inreflection measurements being used to inform the coating process.

In FIG. 22, mobile coating apparatus 1100 is shown in a side view.Mounted on the rear side of chassis 1101 of the mobile coating apparatusis reflectance sensor 1102. Also shown affixed to chassis 1101 iscoating head 1103 and motor 1104 that is coupled to wheel 1105.Reflectance sensor 1102 is shown as a side sectional view, revealinginternal components. These components comprise light source 1106 andphotodetector 1107, where source 1106 shines a wide beam of light makinga spot size with a cross-sectional area of at least 1 cm2, on thesurface of substrate 1110. Light is reflected from substrate 1110 tophotodetector 1107.

As specified above, photodetector 1107 may be a spectrometer adapted toscan over a range of wavelengths, or a photodiode or phototransistorthat integrates light intensities over a large range of wavelengths. Asdescribed above, the raw signal from photodetector 1107 is fed to signalprocessing board 1108, comprising a microprocessor and an on-boardmemory. The microprocessor may execute algorithms stored in on-boardmemory that digitize the analog signal to binary data, then analyze thedata as photometric measurements such as spectral data, or overallreflectance data to show changes in surface reflectance before and afterapplication of a coating solution by the coating apparatus. The analysisroutines may require baseline data for comparison, thus requiring ameasurement of the uncoated substrate or of a previously coatedsubstrate. Before-and-after data may be compared, and changes in thespectral characteristics or reflectance values may be correlated tocoating characteristics, such as film thickness.

For this conclusion, a look-up table may be employed by themicroprocessor, or calculation formulas may be employed as part of thealgorithm. As an example, a red shift in the reflectance spectrum mayindicate that the film is too thick. The algorithms may then generatefeedback control data that may be output as human-readable values, or ascommand signals to motor drive electronics, forming a closed controlloop with the motor drive. Referring to FIG. 22, signal processing board1108 is shown in electronic communication with drive electronics ofmotor 1104 via signal cable 1109. The command signals may command themotor to slow down, since the film thickness decreases at slower speedsof the mobile coating apparatus.

FIG. 23 details a schematic of the instant innovation as described.Portable sensor system B100 is shown in active deployment as a portabledevice, where it is disposed on a substrate surface, where substrateB101 is undergoing measurement. Incident light source B102 shines light,which may be substantially broadband light (‘white’ light) or narrowbanded colored light, emanating from a variety of light sources. Forinstance, incandescent light sources may be used having coatingsyielding different IR and visible spectra, or black body temperatures,as is commercially available with incandescent bulbs. Other sources maybe used as well, such as mercury lamps, inert gas glow discharge (coldand heated cathode) sources, LED or laser sources. In addition, ‘white’light sources using bandpass or cutoff filters may be employed. Thechoice may be dictated by the desired spectral range of the incidentlight. Light rays are shown incident on substrate B101, and reflectedspecularly to photodetector B103.

Additional embodiments of this innovation may include multiple lightsources of the same or different types and multiple photodetectors ofthe same or different types. The different types may be used to detectmore accurately particular wavelengths of interest. For example, a lightsource and/or photodetector tuned to more accurately identify bluewavelengths in conjunction with a light source and/or photodetectorstuned to more accurately identify green and or red wavelengths mayprovide accurate information about the characteristics of the coatingwithout having to integrate over the whole spectrum. Such speciallytuned light sources and/or photodetectors may operate in parallel orsequentially to each other in the measurement process.

This is shown in FIG. 23, where secondary photodetector B104 ispositioned to gather peripheral light emanating from source B102.Signals from photodetectors B103 and B104 are routed to signalprocessing board B105 via cables B106. Board B105 is also in electronicor electrical communication with light source B102 via a cable B106. Inaddition, board B105 is in electronic communication with display B107.An additional output port B113 is shown on board 105, where output portmay be a USB port, RS232 port or a parallel port for data exchange withan external computing device. In other embodiments, a wirelesscommunication IC, such as a Bluetooth, cellular or Wi-Fi IC may also beincluded for wireless communication with an external computing device orthe internet.

In other embodiment of this innovation, one or more secondaryphotodetectors may be used in conjunction with the primary photodetectorto measure and monitor the light output from the one or more lightsources themselves, and feed data back to the microprocessor in order tocorrect for light source fluctuations or light source drift that canchange the reflection measurements This is shown in FIG. 23b , wherephotodetector B103 is replaced by lens B108. Lens B108 gathers reflectedlight and focuses it to the entrance of an optical fiber coupler B109.Light is then guided via optical fiber B110 to spectrometer orspectrophotometer B111, which is shown to be tied to board B105 viacable B106. Board B105 may comprise a microprocessor that reads spectraldata from spectrometer B111 on command. Other embodiments of the instantinnovation may comprise a combination of spectrometer B111 andphotodetector B103. An example of a suitable miniature spectrometer tofulfill this role is an Avantes AvaSpec Micro, the STS Microspectrometerfrom Ocean Optics, to name a few of a number of suitable devices.

In FIG. 23a , the basic schema of the innovative portable sensor isagain shown, with substrate B201 illuminated by light source B202, andreflecting light to photodetector B203, which feeds its signal to signalprocessing board B204. According to the innovation, the spot sizecross-sectional area is at least 1 cm2 in area. In FIG. 23b , a zoomview of the region illuminated by the incident light is shown. Theilluminated region has a plurality of non-uniformities in a portion ofcoated substrate, where a plurality of small asperities and thin areasare present, resulting in micro-variations of coating thickness. In thisembodiment, photodetector B203 is not adapted to spatially resolve thelight impinging upon it. Individual light rays reflected from thetotality of these micro-variations may be integrated when collected atthe photodetector B203 such that the intensity variations in theindividual light rays are spatially averaged as to a single signallevel. Photodetector B203 may comprise a spectrometer, adapted toresolve light intensity as a function of wavelength. Alternatively,photodetector may comprise a photodiode or phototransistor adapted toyield a voltage level corresponding to the averaged light intensity ofthe reflected light. Filters, such as bandpass or cutoff filters, mayfurthermore be used to block portions of the light spectrum inconjunction with a photodiode or phototransistor detectors toapproximate a spectrometer.

Referring again to FIG. 23a , the signal generated by photodetector B203is fed to signal processing circuit 204, which is in electroniccommunication with photodetector 203. In FIG. 24, a coating apparatusB300 of the type described in co-pending U.S. patent application Ser.No. 14/668,956, incorporated herein in its entirety, is shown movingalong substrate 301. The speed and trajectory of coating apparatus B300may be fully manually controlled by a human operator, or may be at leastpartially controlled automatically, with some degree of guidance orhandling by a human operator. Coating apparatus B300 comprises coatingheads B302 and a mounted embodiment of the instant innovation B303. Anarrow shows the direction of travel by apparatus 300. The instantinnovation (portable sensor) B303 is shown mounted on the chassis B304of coating apparatus B300, where it extends over aft or rear portion.

In FIG. 25, a detailed side sectional view of the innovative portablesensor B400 based on the mounted embodiment B203 of FIG. 2. Portablesensor B300 as described in the instant disclosure is shown mounted onthe rear side of chassis B401 of the mobile coating apparatus. Alsoshown affixed to chassis B401 is coating head B402 and motor B403 thatis coupled to wheel 304. Portable sensor B400 is shown as a sidesectional view, revealing internal components. These components compriselight source B405 and photodetector 406, where source B305 shines a widebeam of light making a spot size with a cross-sectional area of at least1 cm2, on the surface of substrate B409. Light is reflected fromsubstrate B409 to photodetector B406.

As specified above, photodetector B406 may be a spectrometer adapted toscan over a range of wavelengths, or a photodiode or phototransistorthat integrates light intensities over a large range of wavelengths. Asdescribed above, the raw signal from photodetector B406 is fed to signalprocessing board B407, comprising a microprocessor and an on-boardmemory. The microprocessor may execute algorithms stored in on-boardmemory that digitize the analog signal to binary data, then analyze thedata as photometric measurements such as spectral data, or overallreflectance data to show changes in surface reflectance before and afterapplication of a coating solution by the coating apparatus. The analysisroutines may require baseline data for comparison, thus requiring ameasurement of the uncoated substrate or of a previously coatedsubstrate. Before-and-after data may be compared, and changes in thespectral characteristics or reflectance values may be correlated tocoating characteristics, such as film thickness.

For this conclusion, a look-up table may be employed by themicroprocessor, or calculation formulas may be employed as part of thealgorithm. As an example, a shift in the reflectance spectrum towardsthe red or infrared side of the light spectrum may indicate that thefilm is too thick. The algorithms may then generate feedback controldata that may be output as human-readable values, or as command signalsto motor drive electronics, forming a closed control loop with the motordrive. Referring to FIG. 25, signal processing board B407 is shown inelectronic communication with drive electronics of motor B403 via signalcable B408. The command signals may command the motor to slow down,since the film thickness decreases at slower speeds of the mobilecoating apparatus.

An embodiment of the above description is shown more explicitly in thediagram of FIG. 26, showing a control system B500 for a mobile coatingapparatus, for example, as described in co-pending U.S. patentapplication Ser. No. 14/668,956, the contents of which are incorporatedherein in their entirety. The exemplary mobile coating apparatus controlsystem B500 may be governed partially or fully by microprocessor B501,which may be physically incorporated on signal processing board B502.

Microprocessor B501 is shown to be in electronic communication with bothphotodetector/spectrometer B503 and motor controller electronics board504. Analog voltage or current signals issuing fromphotodetector/spectrometer B503 may be digitized to binary code by ananalog to digital converter (ADC) unit residing on photodetector B503itself, or by an ADC integrated on the microprocessor chip, or by aseparate ADC unit residing on signal processing board 502. Raw analogsignals generated by photodetector/spectrometer B503 may constitutephotometric data, wherein the photometric data may comprise spectralinformation, or at least integrated light intensity information. Thephotometric data in turn relate characteristics of the coating, in theuncured or cured state, such as total reflectance, spectral reflectance,and indirect measurements such as film thickness and roughness.Conversion of photodetector signals into binary format may constitutephotometric data, read by microprocessor B501.

Consequently, microprocessor B501 may issue motor control commandsgenerated by one or more algorithms embodied in software stored in a RAMor ROM accessible by microprocessor B501, where the algorithms processthe output of photometric data from photodetector/spectrometer B503.Commands issued by microprocessor B501 may be received by motor controlelectronics board B504 in the form of continuous analog voltage levelsor voltage pulses to drive a stepper motor or a dc motor, either typeshown schematically by motor 505. Both motor direction and speed may becontrolled by motor control electronics board B504. The controlcircuitry constitutes a closed-loop embodiment of the mobile coatingapparatus control system, which is automatic control based on decisionsmade by algorithms embodied in the software executed by microprocessorB501.

In another embodiment, the mobile coating apparatus control system maybe an open-loop control system. Microprocessor B501 is also shown to bein electronic communication with human-readable display B506, whereasmotor control electronics board B502 is shown also to be in electroniccommunication with manual motor control console B507. In the open-loopcontrol scheme, a human operator may read output displayed onhuman-readable display B506, which may be a serial or parallel input LCDdisplay. In the example shown in FIG. 26, a selection switch B508 isprovided to select between manual control or microprocessor control ofthe motor controller electronics. To facilitate manual coating processcontrol, the analysis algorithms embodied by software stored on a RAM orROM accessible to microprocessor B501 may be adapted to communicateprocess optimization recommendations that are electronically displayedto the human operator, using human-readable display B506 disposed on ahand-held or apparatus-mounted innovative portable sensor, as anexample. Microprocessor B501 may also be in electronic communicationwith a wireless network interface (not shown) adapted to transmit dataover the internet wirelessly in some embodiments for display on acomputing device.

Characters output from microprocessor B501 to human-readable displayB506 may be in a format understandable to the human operator, andindicate, for example, recommendations of motor speed and/or directionmay be controllable by the human operator, in order to maintainoptimized coating quality. The decision as to what speed the apparatusshould be travelling along the substrate, for example, may be based onphotometric data generated by photodetector/spectrometer B503. By way ofexample, the photometric data may indicate coating thickness, which maybe dependent on the speed of the apparatus. These recommendations mayalso include exhortations to decrease the viscosity of the coatingsolution, and or change the make-up coating to optimize coatingperformance. In the open-loop control embodiment, control data areoutput to the human operator by means of human-readable display B506.The human operator may read and interpret the control data, and controlthe speed and direction of motor B505 by means of manual motor controlconsole B507. Rotary manual speed control B509 may comprise apotentiometer or a rotary encoder. Other forms of manual control may beused, such as a linear slider potentiometer. Double throw switch B510may be manipulated to control motor direction, causing the mobilecoating apparatus to advance in the forward direction or reverse.

EXAMPLE OF METHOD OF USE

An example of how the instant innovation is employed will now bedescribed. A substrate such as a photovoltaic panel may be deployed inan array or individually in an outdoor setting. It is desired toretrofit the panel with an anti-reflective coating, for which a coatingapparatus of the type disclosed in co-pending U.S. Non-provisionalpatent application Ser. No. 14/668,956 is provided. This coating devicemay comprise wheels and coating heads such that it may be deployed toroll over a photovoltaic panel and deposit a liquid coating pre-cursorsolution that is to be cured after application.

An operator equipped with a portable version of the innovative portablelight reflectance sensor may deploy it on the panel surface before thecoating is applied, to obtain a baseline measurement of percentreflection of incident light as the photometric data. After the baselinemeasurement, the coating is applied by the coating apparatus. A secondpercent reflection measurement is then taken. Data from bothmeasurements are digitized by the signal processing circuit and storedin an on-board memory.

The data are then processed by the signal processing circuitry on-boardthe instant portable sensor, as described above, where the twomeasurements are compared. A change in percent reflection obtained, withdata from the second measurement correlated to the state of the newlyapplied coating solution. The signal processing circuit then displaysthe information to the operator. If the coating is too thick or thin,instructions or recommendations are displayed to the operator as amethod of feeding back to the operator in control to adjust the speed ofthe coating apparatus, or to alter the viscosity of the coatingsolution. The information may also be conveyed by connection to a laptopcomputer, or wirelessly to a smart phone in possession of the operatorat the site, or to personnel at a remote site.

The embodiments of the innovation disclosed and described above areexemplary, and by no means are meant to be construed as limiting theinnovation. It is recognized by persons skilled in the art that othervariations are possible without departing from the scope and spirit ofthe innovation, as claimed in the claims below.

The tunable coating property aspect of the instant invention may bederived in part through variations in the deposition process, preferablyby varying the thickness of the coating. The tunable coating propertyaspect of the instant invention may be derived in part from variation ofthe final composition of the coating, which in turn is determined by therelative amounts of precursors in the wet coating precursor solution, orprecursor ratio, can be selected from a continuum of precursor ratiosdisclosed herein to produce desired coating characteristics. Preferably,the concentration of the siloxane component is changed to yield desiredproperties. Siloxanes or hardcoats are available through a variety ofmanufacturers. An example of a hardcoat is poly dimethyl siloxane (PDMS)and derivatives.

Formulation

The dry content composition of the inventive AR coating may comprise thefollowing composition ranges in terms of solids content (dry weightpercentages):

-   -   Matrix/Silicate: 60-100%    -   Siloxane: 0-20%    -   Nanoparticles (hollow and/or solid): 0-20%        More preferably, the dry composition may comprise the following        ranges:    -   Matrix/Silicate—76-90%    -   Siloxane—5-12%    -   Hollow NP—5-12%

General Coating Precursor Solution

The matrix sol gel precursor is derived from base-catalyzed hydrolysisof an organic orthosilicate, for example tetramethyl orthosilicate(TMOS) or tetraethyl orthosilicate (TEOS). Sol gel creation from organicorthosilicates such as TMOS and TEOS is well known in the art, and theexact concentrations and final pH adjustments of the acid and basecatalysts can vary. Many examples of particular conditions can be foundin both the patent and scientific literature.

One embodiment of the coating precursor solution is formulated as amixture of the following at room temperature:

-   -   Organic orthosiicate (TMOS) sol gel concentration can range up        to 50% in alcohol—base-catalyzed.    -   Hardcoat siloxane concentration can range up to 50% in alcohol    -   Hollow-spherical nanoparticle (HSNP) concentration can range up        to 50% as an alcoholic suspension.        wherein the alcohol may comprise any one of C1 to C10 alcohols        and mixtures thereof. Any suitable solvent known to those        skilled in the art may be used.        The volumetric ratios of the individual coating precursor        solutions may be adjusted to yield precursors having the        following concentrations based on ratios of one to the other or        final percentages in solution:    -   HSNP 0-20%    -   Hardcoat 0-20%

Example of Low Temperature Curing AR Coating Composition

A low temperature curing AR coating solution composition comprises thefollowing components. Base-catalyzed orthosilicate tetramethylorthosilicate (TMOS-b) system is prepared, by mixing TMOS, water,methanol or ethanol, and a base catalyst that may include any of thefollowing basic compounds: ammonia, organic amines (RNH₂, R₂NH, R₃N,where R=C₁₋₃ alkanes), basic amino acids (arginine, lysine) andquaternary ammonium halides, preferably where the quaternary ammoniumion has the formula RNMe₃, where R=C₆₋₁₂ alkanes. Preferably, apre-mixture of 4:1 TMOS-b:binding agent is prepared. TMOS-b tends topolymerize into long linear chains and does not extensively cross-link.Preferably, a binding agent that undergoes hydrolysis during curing,forming linear or branched structures at low temperature, occurringreadily under 100° C., is added as well. In the inventive energytransmission enhancement coating composition, the binding agent may beused as a minority reagent in combination with TMOS-b to provide for thecross-linking of the long linear silicate chains made by thepolymerization of TMOS-b. The combination of the binding agent andTMOS-b in the composition disclosed advantageously cures to form hardscratch resistant coatings at substantially lower temperatures for lesscuring time than previously disclosed coatings of similar composition.

The novel AR coating composition further comprises organosilaneadditives for improvement of hydrophobicity, and any of theorganosilanes having the structure (R₁)_(n)Si(OR₂)_(4-n)(R₁, R₂: C₁₋₃alkane, alkene, n=0-3) and RSiCl₃ (R: C₁₋₃ alkane, alkene) have beenfound to may be added in varying ratios to the binder:TMOS-b mixture.Optical properties of the coatings are controlled using both solid andhollow sphere silica nanoparticles, described below. In otherembodiments, no nanoparticles are added to the mixture. Lowtemperature-curable coatings according to the invention form hightransmittance and excellent abrasion resistance (see FIGS. 8-10) whencured at, for example, 40° C. for 24 hours, 50° C. for 8 hours, 65° C.for 4 hours, 150° C. for 1 hour,. This contrasts more typical curingregimes of curing temperatures ranging between 90° C. -700° C. for 10minutes or less for the higher temperatures, up to five hours for thelower temperatures. Such a treatment may yield a film thickness rangingbetween 50-250 nm. Other thermal treatment regimes, as well as moreexotic plasma and microwave methods are not excluded.

Formulations for the low temperature AR coating solution compositionsmay comprise the following ranges:

-   -   Without nanoparticles    -   TMOS-b (Matrix/Silicate): 50-95%    -   Binder: 5-50%    -   With nanoparticles    -   TMOS-b (Matrix/Silicate): 60-90%    -   Binder: 5-20%    -   Nanoparticles (hollow and/or solid): 5-20%

Nanoparticle Addition

It may be desired to incorporate added hollow silica nanoparticles tothe precursor coating solution. Syntheses of hollow spherical silicananoparticles are well known in the art. Many examples of silica HSNPcan be found in both the patent and scientific literature. Procedures tosynthesize hollow nanoparticles are abundant in the patent andscientific literature. In terms of size, the hollow nanoparticles canrange between 5 to 200 nm. In terms of distribution, the hollownanoparticles can be within a narrow size range, or within in a bimodalsize range, a trimodal size range, multimodal or completely random sizedistribution. In addition to hollow nanoparticles, solid nanoparticlesmay be incorporated into the film. One such method is to procure solidnanoparticles from a commercial source and incorporate them into thesolution mix prior to making the film.

Incorporation of pre-synthesized nanoparticles creates additional coststo manufacture the innovative coating precursor solution. Preferably,the instant coating precursor solution does not incorporate the additionof pre-synthesized nanoparticles, and instead produces a coating wherenanoparticles may form spontaneously.

Example of Coating Panel Substrates on in the Field

The coating deposition comprises mixing the individual coating precursorcomponents together to form the coating solution. The coating solutionis then deposited on a substrate using a coating apparatus adapted tocoat substrates such as photovoltaic panels and solar thermal panelsalready existing in a field installation. Such a coating apparatus isdescribed in detail in the US Utility Patent referenced earlier andincorporated herein by reference in its entirety, but coatingapparatuses for the purpose of this disclosure are not limited to anyparticular type, and in general comprise a coating distribution means.The coating distribution means include, but are not limited to, spraycoating nozzles, brushes and contact applicators of the like. This pointis explained below. By virtue of the capability of the inventive coatingprecursor solution to cure at temperatures well under 100° C., theability to retrofit or re-coat substrates in existing installations withan optical coating, such as an antireflective coating, is provided. Thisimprovement eliminates the need to dismantle the substrate from theinstallation to send it to the factory of origin or to a specialfacility for coating, avoiding a costly and disruptive maintenanceprocedure. The installations referred to in this disclosure comprise asingle substrate, such as a single individual photovoltaic panel, or anarray of multiple panels, as in a photovoltaic array. The term “array”is meant to be understood to consist of a single panel or multiplepanels. Substrates may be extended to include solar thermal panels,regarded individually (single panel arrays) or in multi-panel arrays. Inaddition, glass window panes installed in residential and commercialbuildings are included in the definition of substrate as well for thepurposes of this disclosure.

A coating apparatus may be a standard one known in the art to makethin-film coatings, such as, by way of example, a roll coater, spincoater, dip coater and spray coater. The coating process may be carriedout at ambient temperatures, but temperatures both above and belowambient are not excluded. Coating thickness may be controlled by certaincoating parameters such as the viscosity of the coating solution, speedof a moving substrate, and/or the curing process, as described below.

Most preferably, the coating is applied to a substrate, such as a solarphotovoltaic panel installed in an outdoor photovoltaic array, by use ofthe coating apparatus described earlier. The coating apparatus isadapted to deposit an optical thin-film coating layer of uniformthickness by use of innovative coating heads, or brushes, on substratessuch as photovoltaic panels in both indoor and outdoor installations.For the purposes of this disclosure, the substrate is disposed in anambient, where an ambient can be defined either as an indoor or outdoorenvironment. “Outdoors”, or “out of doors” is defined as being outside,or disposed in the open environment, whereas “indoors” is defined asbeing inside, or disposed in the interior of an enclosed structure, suchas a building. For purposes of this disclosure, “field” is used, such as“field-coated”, to mean the coating process takes place outside of afacility where the substrate would normally be manufactured, and ratherthe inventive coating process occurs in an individual or arrayinstallation of the substrate, typically out of doors.

An example coating procedure is the following:

A substrate is provided, where the substrate can be any one of thefollowing: a photovoltaic panel, a solar thermal panel, a glass pane. Inpractical terms, the substrate may be referred to as a panel or pane,and may be part of an existing installation, either as a single panel ormulti-panel array, for photovoltaic and solar thermal installations, oras glass windows installed in a structure. As discussed above, a coatingapparatus is provided, comprising a coating distribution means. Such acoating distribution means may be based on a brush methodology where thecoating distribution means is an applicator head having one or morebrushes in intimate contact with the substrate surface, applying auniform layer of liquid coating precursor solution on the substrate.Such a coating means is described in detail earlier in thisspecification. Alternatively, the coating distribution means may bebased on a spray methodology, where one or more spray nozzles are usedto apply a uniform layer of optical-coating precursor solution to thesubstrate, where the nozzles are positioned at a distance above thesubstrate surface.

The coating apparatus may be positioned on the substrate surface, whichfor photovoltaic panels or solar thermal panels, may be inclined at anobtuse angle with respect to the vertical. As an example, the coatingapparatus may be placed on the lower end of the panel. The coatingapparatus may be hand-driven, in which case it may have an elongatedhandle attached to it. An operator may then move the coating apparatusalong the substrate surface in an excursion from the initial position tothe upper end of the substrate. For a brush applicator, the one or moreapplicator heads may be engaged on the surface during the excursion.Alternatively, the applicator heads may be engaged during the returnexcursion, or during both excursions. The coating apparatus may also beadapted to move in a grid pattern, being displaced laterally. Theforegoing is also true for a coating apparatus having a spraydistribution means.

A thin film layer of the inventive precursor solution is then applied toeither the entire surface of the substrate, or a portion thereof, with asubstantially uniform thickness. Preferably, the precursor layer is ofsuch a thickness that a cured coating thickness of 50-250 nm willresult. Moreover, the coating may be deposited in a single pass or bymultiple passes, where the same or different coating precursor solutionis deposited over a previous coating layer of the same composition. Inpreferred embodiments, the innovative coating is prepared as asingle-pass layer or a double-pass layer. Preferably, the coatingapparatus is motorized, where a motor drive is engaged with the tractionmeans of the coating apparatus, and provides a constant speed oftranslation of the apparatus. The constant speed is preferable, as therate of deposition of the layer is a strong function of the speed oftranslation of the apparatus. By precise control of the speed of thecoating apparatus during its coating excursions, the final thickness ofthe layer is well controlled and spatially uniform. This is best done bya motorized coating apparatus. In this manner, the thickness may readilybe tuned to ¼ wavelengths of target portions of the solar spectrum orother ambient lighting. Alternatively, the thickness may be tuned toanother optimum thickness or thickness range favoring the performanceenhancing characteristics of the coating.

The precursor layer may now undergo a curing step, wherein thesubstrate, as part of an outdoor installation, is passively cured out ofdoors in the sun at ambient temperatures. Preferably, the substratesurface temperatures range from 10° C. to over 100° C. Surfacetemperatures such as those figuring in the quoted range may beengendered by ambient sunlight, and related to air temperature, which isprimarily dictated by weather conditions, season and geographiclocation. According to the innovation, the warmer the substrate surfacetemperature, the faster the curing process occurs.

Alternatively, the curing process may take place under conditions of lowlight levels, or in the dark entirely, as the curing chemistry is athermal process. As an example, a coated substrate in an outdoorinstallation may be cured under cloud cover, or at night. Moreover, thesubstrate may be cured indoors, where the surface temperature isapproximately the ambient temperature.

The surface in the case of the photovoltaic film is uneven, but theinnovative coating forms a smooth optical film. The innovative coatingis a single layer coating, as explained above, being substantiallycompositionally homogeneous across its thickness.

Optical Performance

The effect of using the inventive AR coating on glass and plasticsubstrates is shown in FIGS. 5-7. In FIG. 28, the visible wavelengthtransmission spectra are shown for a smooth flat window glass substrate.The upper curve represents the glass substrate coated with the inventiveenergy transmission enhancement coating, in this case intended as an ARcoating, on one side. The data show an improvement of transmission(Delta T) of up to 4% between 500 and 600 nm, and minimum 3% elsewhere,with an average gain in transmittance of 3.65%.

Direct reflectance measurements on textured glass are shown in FIG. 29.Here, the data show the decrease in reflected light (upper graph, dashedcurve) across the visible spectrum due to the presence of the inventiveenergy transmission enhancement coating. The average decrease is 3.73%.In the lower graph of FIG. 29, the dashed curve represents the change inreflectance from the surface of the substrate coated with the innovativecoating.

FIG. 30 shows the effect of the inventive energy transmissionenhancement coating on both sides of an acrylic (PMMA) substrate. Thecomparison between the coated transmission spectra of a PMMA substratewith the innovative coating (dashed curve) to the same substrateuncoated (solid curve) is shown in the upper graph. The lower graph ofFIG. 30 shows that the inventive coating resulted in an average increaseof transmittance of 6.75% across the visible spectrum from 400 to 750nm.

Abrasion resistance of the low-temperature curable energy transmissionenhancement coating is demonstrated in FIG. 31. The abrasion scrub testexperiments were carried out with 2000 strokes of a brush meeting ASTMD2486 standards with 500 g of force over the coating. FIG. 31 shows thetransmission spectrum of a single layer of the inventive AR coating overthe wavelength range between 400-900 nm, before and after the abrasiontest, where the solid red curve represents the spectrum of a virginsingle-pass coating before the abrasion resistance test, and the brokencurve was measured after the abrasion test.

FIG. 32 compares the change in transmittance over the indicated spectrumfor the coating before and after the abrasion test. The data show only a0.3% average decrease in the transmission of light after completion ofthe abrasion resistance test, indicating that over 90% of the virginfilm was retained after the test, therefore demonstrating that thesingle-layer film has a high degree of scratch resistance. The lowersolid curve represents the transmission spectrum of the bare glasssubstrate, showing that the AR coating provides for an average of a 3.5%increase in light transmission through the substrate, almost fullsuppression of reflection by the novel AR coating.

FIG. 33 shows results from the same abrasion scrub test applied to adouble-pass energy transmission enhancement coating. Again, the solidred curve shows the transmission spectrum of the virgin double-layercoating, and the broken curve is the resulting transmission spectrumafter the abrasion test. The data here show that the change in theoptical characteristics is only about 0.09%, indicating over 97% of thecoating was retained. The results here demonstrate that the double-layercoating exhibits a greater degree if robustness than the single-layer.

The moisture degradation performance of the inventive films is measuredand shown in FIG. 34. The data in this figure are taken from subjectingthe inventive AR coatings to conditions dictated by theindustry-standard Highly Accelerated Stress Test (HAST). In this test,the coatings were subjected to high temperature of 140 C, 85% humidityat approximately 30 psi (2 atmospheres) of pressure. Under theseconditions, the HAST test simulates humidity degradation over a 20 yearperiod. The solid red curve of FIG. 34 is the optical transmissionspectrum of the coating on a glass substrate before the test. The bluecurve is the transmission spectrum of the coating after the test,whereas the lower solid curve is the transmission spectrum of the bareglass substrate. The results here show that the before and after changeof transmission characteristics of the coating is about 0.06%, whichindicates that over 98% of the coating was retained after the HASTprocess.

While the forgoing embodiments disclosed above describe the invention inits various manifestations, the foregoing embodiments are to beunderstood by persons skilled in the art as exemplary in nature, and arein no way intended to be construed as the only embodiments possible forthe invention. Those skilled in the art will also understand that otherembodiments and examples of deployment of the inventive AR coatings areconceivable and possible without departing from the scope and spirit ofthe invention.

What is claimed is:
 1. An apparatus for forming a nanostructuredperformance enhancement thin film coating on an array of sloped outdoorpanel surfaces comprising: A. A meniscus drag coating applicatorcomprising: i. at least a first meniscus drag deposition mechanism andat least a second meniscus drag deposition mechanism for depositing aperformance enhancement coating solution onto the sloped outdoor panelsurfaces, with each meniscus drag deposition mechanism comprising: a. atleast two materials of different capillary attraction for theperformance enhancement coating solution, wherein one material has alower capillary attraction for the performance enhancement coatingsolution than the other material; b. a mechanism for raising andlowering the meniscus drag deposition mechanism so that it contacts thesurface of the outdoor panels in the lowered position and does notcontact the surface of the outdoor panels in the raised position; c. atleast one fluid manifold for distributing the performance enhancementsolution to the at least one material of lower capillary attraction,wherein the solution transfers from the manifold to the lower capillaryattraction material and then the solution transfers from the lowercapillary attraction material to a higher capillary attraction material,wherein the solution transfers from the higher capillary attractionmaterial to the sloped outdoor panel surfaces as the one or moremeniscus drag deposition mechanisms are moved across the sloped outdoorpanel surfaces; at least one pump connected to tubing that transfers thesolution from at least one fluid reservoir to the at least one manifold;iii. a means of moving at least one meniscus drag deposition mechanismsacross at least a portion of the sloped outdoor panel surfaces duringone or more coating passes of the one or more meniscus drag depositionmechanisms across at least a portion of the sloped outdoor panelsurfaces; iv. one or more rolling mechanisms to move the applicatoracross the sloped outdoor panel surfaces, wherein at least one or moreof the roller mechanisms is oriented in such a way as to ensure theapplicator remains engaged with the sloped outdoor panel surfaces anddoes not slide off; v. wherein the first meniscus drag depositionmechanism is mounted to a first side of the coating applicator and thesecond meniscus drag mechanism is mounted apart from the first meniscusdrag deposition mechanism on a second side of the applicator oppositethe first side of the applicator, wherein the one or more of the rollingmechanisms is positioned between the first meniscus drag depositionmechanism and the second meniscus drag deposition mechanism; vi. whereinan algorithm determines how far to move the applicator between the oneor more coating passes, the algorithm comprises the following steps: a.aligning the first meniscus drag deposition mechanism with an uncoatedarea to be coated; b. lowering the at least first meniscus dragdeposition mechanism so that it contacts the surface of the outdoorpanels; c. performing a coating pass; d. raising the at least firstmeniscus drag deposition mechanism so that it does not contact thesurface of the outdoor panels; e. moving the applicator so that thefirst meniscus drag deposition mechanism is aligned with a subsequentuncoated area to be coated; f. lowering the at least first meniscus dragdeposition mechanism so that it contacts the surface of the outdoorpanels; g. performing a coating pass; h. raising the at least firstmeniscus drag deposition mechanism so that it does not contact thesurface of the outdoor panels; i. moving the applicator so that thefirst meniscus drag deposition mechanism passes by a surface portionthat was previously coated by the at least second meniscus dragdeposition mechanism to a further subsequent uncoated area to be coatedby the first meniscus drag deposition mechanism; j. lowering the atleast first meniscus drag deposition mechanism so that it contacts thesurface of the outdoor panels; k. performing a coating pass; l. raisingthe at least first meniscus drag deposition mechanism so that it doesnot contact the surface of the outdoor panels; and m. repeating thealgorithm; B. a mechanical extension device that enables at least thefirst meniscus drag deposition mechanism or the second meniscus dragdeposition mechanisms to run off at least one end of at one of thesurfaces of the sloped panels, wherein the mechanical extension deviceis integrated with the applicator; C. a sensor for sensing thetemperature of the sloped outdoor panel surfaces; D. wherein a speed ofthe one or more meniscus drag deposition mechanisms is dependent on thetemperature of the sloped outdoor panel surfaces, wherein the speed ofthe one or more meniscus drag deposition mechanisms is reduced if thetemperature of the sloped outdoor panel surfaces decreases.
 2. Theapparatus of claim 1, wherein the speed of the one or more meniscus dragdeposition mechanisms is changed to optimize optical characteristics ofthe nanostructured performance enhancement thin film if the spectrum ofthe reflected light from the nanostructured performance enhancement thinfilm shifts relative to the red or infrared side of the light spectrum.3. The apparatus of claim 1, wherein the first meniscus drag depositionmechanism may be raised or lowered independently of the second meniscusdrag deposition mechanism.
 4. The apparatus of claim 1, wherein thenanostructured performance enhancement thin film coating is ananti-reflection coating.
 5. The apparatus of claim 1, wherein theapparatus further comprises at least one sensor for sensing reflectedlight from the nanostructured performance enhancement thin film coatingafter it is deposited on the sloped outdoor panel surfaces.
 6. Theapparatus of claim 5, wherein the sensor for sensing the reflected lightfrom the nanostructured performance enhancement thin film coating isattached to the meniscus drag coating applicator.
 7. The apparatus ofclaim 5, wherein the sensor for sensing the reflected light from thenanostructured performance enhancement thin film coating is portable,and able to be moved independently of the meniscus drag coatingapplicator.